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Critical Path Method (CPM) in Project Management

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What Is the Critical Path In Project Management?

What is the critical path method (cpm), cpm vs. pert, when should you use critical path analysis, what is the importance of cpm in project management, critical path diagram, critical path method (cpm) formula, critical path method example, critical path method steps.

• Benefits of Using CPM In Project Management

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Cpm & project management software, must-have features of critical path software.

• How to Find the Critical Path with ProjectManager

In project management, the critical path is the longest sequence of tasks that must be completed to execute a project. The tasks on the critical path are called critical activities because if they’re delayed, the whole project completion will be delayed. To find the critical path, project managers use the critical path method (CPM).

The critical path method (CPM) is a project management technique that’s used by project managers to create an accurate project schedule . The CPM method, also known as critical path analysis (CPA), consists in using the CPM formula and a network diagram to visually represent the task sequences of a project. Once these task sequences or paths are defined, their duration is calculated to identify the critical path.

Related: 12 Free Project Scheduling Templates for Excel

Finding the critical path is very helpful for project managers because it allows them to:

• Accurately estimate the total project duration.
• Estimate the time that’s necessary to complete each project task.
• Identify critical activities which must be completed on time and require close supervision.
• Find out which project tasks can be delayed without affecting the project schedule by calculating slack for each task.
• Identify task dependencies, resource constraints and project risks.
• Prioritize tasks and create realistic project schedules.

Once done by hand, the critical path can now be calculated automatically with project scheduling software equipped with Gantt charts , which makes the CPM method much easier. ProjectManager is project management software that helps you quickly implement the critical path method. Build a project schedule on our award-winning Gantt chart, then simply filter for the critical path. When it’s time to execute, your team can collaborate with a task list, kanban board or calendar. And you can track everything with dashboards and reports to ensure you stay on track. Get started today absolutely free.

ProjectManager can calculate the critical path for you on our award-winning Gantt charts— learn more .

The critical path method was developed in the late 1950s by Morgan R. Walker and James E. Kelley. The origins of the critical path method are closely related to the Program Evaluation and Review Technique (PERT), a similar method that is commonly used in conjunction with CPM in project management .

The critical path method (CPM) and program evaluation and review technique (PERT) are both project scheduling techniques. But they aren’t interchangeable. We’ve been talking about CPM, but before we compare it to PERT let’s define the term.

PERT is used to get accurate time estimates for complicated projects. It uses an algorithm to calculate the estimated duration for unpredictable activities. It focuses on events and milestones on a PERT chart with nodes in the wireframe when developing projects.

However, while these are two different techniques, PERT and CPM can be used together for project planning and scheduling. The difference between them lies in that PERT is about time planning and time management, while CPM is about time and budgeting. PERT delivers a project quickly and CPM gets the project done on budget and on time.

Now that we know what’s the critical path of a project, we can learn about the critical path method (CPM), an important project management technique that’s based on this concept.

Critical path analysis is another way of referring to the critical path method. As noted, it’s used by industries with complex projects, such as aerospace, defense, construction and product development.

Therefore, critical path analysis is a crucial first step in developing a project schedule. It’s done early in the life cycle of a project, usually in the planning phase , but it’s not unheard of to have CPM as part of a project proposal before the project has been approved.

By understanding which are the critical tasks in a project you can focus on getting those done if time, resources and costs are an issue. Knowing this in advance of executing a project will help you deliver that project successfully.

Related: Free Project Plan Template

Projects are made up of tasks that have to adhere to a schedule in order to meet a timeline. It sounds simple, but without mapping the work, your project scope can quickly get out of hand and you’ll find your project off track.

Using the critical path method is important when managing a project because it identifies all the tasks needed to complete the project. It then determines the tasks that must be done on time, those that can be delayed if needed and how much float or slack you have.

When done properly, critical path analysis can help you:

• Identify task dependencies, resource constraints and project risks
• Accurately estimate the duration of each task
• Prioritize tasks based on their float or slack time, which helps with project scheduling and resource allocation
• Identify critical tasks that have no slack and ensure those are completed on time
• Monitor your project progress and measure schedule variance
• Use schedule compression techniques like crash duration or fast tracking

As you can see in this critical path diagram, project activities are represented by letters and the critical path is highlighted in green. Tasks F, G and H are non-critical activities with float or slack. We can also identify task dependencies between the critical path activities, and also between activities (A, F and G) or (A, H and E), which are parallel tasks.

Before we learn how to use the CPM formula, we need to understand some key CPM concepts.

• Earliest start time (ES): This is simply the earliest time that a task can be started in your project. You cannot determine this without first knowing if there are any task dependencies
• Latest start time (LS): This is the very last minute in which you can start a task before it threatens to delay your project timeline
• Earliest finish time (EF): The earliest an activity can be completed, based on its duration and its earliest start time
• Latest finish time (LF): The latest an activity can be completed, based on its duration and its latest start time
• Float: Also known as slack, float is a term that describes how long you can delay a task before it impacts its task sequence and the project schedule. The tasks on the critical path have zero float because they can’t be delayed

The critical path method formula has two parts; a forward pass and a backward pass.

Forward Pass in CPM

Use the CPM diagram and the estimated duration of each activity to determine their earliest start (ES) and earliest finish (EF). The ES of an activity is equal to the EF of its predecessor, and its EF is determined by the CPM formula EF = ES + t (t is the activity duration). The EF of the last activity identifies the expected time required to complete the entire project.

Backward Pass in CPM

Begins by assigning the last activity’s earliest finish as its latest finish. Then the CPM formula to find the LS is LS = LF – t (t is the activity duration). For the previous activities, the LF is the smallest of the start times for the activity that immediately follows.

Let’s take a look at a critical path example to better understand how the critical path method is used in project management. Although it’s high-level, it can help you visualize the meaning of a CPM schedule .

We’ll use this critical path diagram to explain the elements that make up the critical path analysis process. To keep things simple, we’ve already done the calculations for this example using the CPM formula.

The above critical path method example shows the critical path for getting a website online. All the tasks that are scheduled to build and launch the website are shown in the rectangular nodes.

Some of the tasks are being done at the same time as others. For example, the work on defining a target market is being done as the design is being done and the content for the site is being drafted.

However, not all these tasks are equally important. Some aren’t critical to getting the site live by the deadline. That’s where the critical path comes in. It has identified by the colored arrows all the tasks that must be done in order to complete the project plan on time.

Now that you know the key concepts of the critical path method, here’s how to calculate the critical path in 8 steps.

1. Collect Project Activities

Use a work breakdown structure to collect all the project activities that lead to the final deliverable.

2. Identify Task Dependencies

Determine which tasks are dependent on other tasks before they can begin. Use your judgment and your team members’ feedback. Failing to define task dependencies correctly makes the critical path method useless.

3. Create a Critical Path Diagram

A CPM diagram or network diagram , depicts the order of activities.

4. Estimate the Timeline

To use the critical path method, you’ll need to estimate the duration of each task. Use data from past projects and other sources of information such as subject matter experts.

5. Use the Critical Path Formula

The critical path uses an algorithm, also referred to as the CPM formula. That algorithm has two parts, the forward pass and the backward pass. The forward pass is determined by using the earliest start for each activity (ES) and the earliest finish (EF). The ES of an activity equals the EF of the one before it. The EF is calculated by EF = ES + t (the duration of an activity).

The backward pass assigns the last activity’s EF as its latest finish. Then use the CPM formula to find the LS, which is LF – t. For the activities before that, LF is the smallest of the start times for the next activity.

6. Identify the Critical Path

The activities with 0 float make up the critical path. All of these critical path activities are dependent tasks except for the first task in your CPM schedule. All project tasks with positive slack are parallel tasks to the critical path activities.

7. Revise During Execution

Continue to update the critical path diagram as you go through the project execution phase. These critical path analysis steps determine what tasks are critical and which can float, meaning they can be delayed without negatively impacting the project schedule. Now you have the information you need to plan the critical path schedule more accurately and have more of a guarantee you’ll meet your project deadline.

You also need to consider other changes or constraints that might change the project schedule. The more you can account for these unexpected events or risks, the more accurate your critical path schedule will be. If time is added to the project because of these constraints , that’s called a critical path drag, which is how much longer a project will take because of the task and constraint.

Benefits of Using CPM in Project Management

There are many reasons to use the critical path method. It’s a great project management tool to help you deliver your project on time and within budget , but we’ve already discussed that at length. Here are some other benefits of using CPM.

Critical Path Analysis Improves Team Communication

It fosters better communication within the project team . Everyone is involved in providing input and that brings the expertise of various project team members together for the better good of the project as a whole. This includes subcontractors, architects, electricians, construction managers, etc.

CPM Helps Prioritize Tasks

Naturally, having determined the critical path is going to help you prioritize your work. You know the tasks that must be done and that gives you wiggle room if there are issues with time or cost. You might not get every activity done, but you’ll get the ones finished that are critical to the project.

CPM & PERT Help Create Accurate Schedules

The critical path method will help you make a more accurate project schedule , especially when you use it in conjunction with PERT charts. You can estimate better and discover areas of risk and prepare to respond to them to avoid costly delays.

CPM & Gantt Charts Help Map Out Project Plans

Another benefit is the visual nature of CPM, especially when mapped on the timeline of a Gantt chart . Having a visual element to communicate the project schedule is always a plus. Not everyone absorbs information in the same way. Visual tools help teams better understand what’s expected of them and when it’s expected.

Do you still have questions about the critical path method? In this video, Jennifer Bridges PMP, explains how to find the critical path using a CPM diagram.

As stated, the critical path method (CPM) was first invented in the late 1950s. During those times, project scheduling software didn’t exist, and project managers had to calculate the critical path manually.

Fortunately, today there are many project management software alternatives that can help with the critical path process. Most of them use Gantt charts to represent CPM diagrams and calculate the critical path, but their feature sets vary greatly. One of the most commonly used project management software to identify the critical path is Microsoft Project . However, it has major drawbacks that make ProjectManager a better choice.

Here are some of the main features that you’ll need as a project manager to properly use the critical path method for your scheduling process.

Link Tasks and Avoid Bottlenecks

Tasks that are dependent on another need to be a part of your critical path calculation. There are four types: those that are start-start, start-stop, stop-start and stop-stop. By identifying these task dependencies , you can avoid bottlenecks later in the project.

Get a High-Level View of Your Progress

Dashboards are an essential feature for keeping track of critical path activities. They provide a window into the project’s performance and progress by collecting data and displaying it in graphs and charts that show various metrics, such as costs, tasks and more.

Make More Insightful Decisions

Keeping track of a project’s critical path as it’s executed is how you stay on track. But if the information you’re gathering is dated, then you’re always going to be playing catch up. With real-time data from a cloud-based CPM software, you’re always seeing the project as it currently is.

Know Your Project Variance

Schedules are always changing as the project is impacted by internal and external forces. To ensure you’re on target, you need to have project management software that’s collecting data and displaying project variance, so you can compare the actual progress against where you’ve planned to be.

Keep a Record of Your Plan

The critical path helps you plan the project, but once you’ve finalized the schedule, you need to set a baseline. This saves the schedule so you can compare it to your actual progress and know if you’re on time, behind or ahead. Any critical path software should have this feature.

See Deep Data on Performance

Reports serve two purposes. They take you deeper into the project and expose insightful data on project variance, timesheets and more, which helps you stay on track. Filtering the results and sharing the reports is a great communication tool for stakeholder presentations.

How to Find the Critical Path With ProjectManager

Figuring out the critical path by hand takes time, and it must be done throughout the project, which is why using project management software streamlines the process. ProjectManager is award-winning software that automates the critical path method process for you.

Our online Gantt chart filters for critical path, links dependent tasks and is integrated into a full project management software. Sign up for a free 30-day trial of our software and follow along to build a dynamic Gantt chart and automatically calculate your critical path in a few easy steps.

1. Start a Project With a Gantt Chart

Managing a project on Gantt charts allows you to both plan and schedule in one place. Add your tasks and their durations, and they’ll automatically appear on a project timeline, allowing you to see your whole project at once.

In the software, upload your tasks manually or upload a pre-existing spreadsheet. Add task descriptions, deadlines, priority, tabs and assign them to one or more team members. We also provide templates to help you get started.

2. Add Task Dependencies

In the software, connect your dependent tasks on the Gantt chart by dragging one onto the other. You’ll see a dotted line indicating that the tasks are linked, and you can then define the type of dependency it is.

3. Set the Project Baseline

Setting the baseline is possible when you’ve finished making your project schedule, complete with deadlines and costs. The baseline captures your data and uses it to compare against your actual progress.

On the Gantt chart, create your baseline for the project by adding the start date to the task and when it’s due to be completed. These planned start and end dates will be compared to your actual project data and show you whether you’re on target.

4. See the Critical Path

Easily find the critical path of your project by using our critical path filter. This helps you know what must be done to complete the project and shows if you’re experiencing any slippage.

5. See Your Overview With a Dashboard

Now that you’ve got your project planned out, viewing it from a dashboard is the best way to get a high-level view of your progress.

From the dashboard view, track if your project is proceeding as planned. Our dashboard monitors several project metrics, such as variance, tasks and more, automatically calculating your data to display it in easy-to-read charts and graphs.

6. Report on Progress

Reporting is crucial to pull data from your project and get and share insights into how it’s doing. Reports come in many varieties, which together provide a snapshot of the whole project’s performance.

Easily generate reports on the critical path, task progress, project status , costs and more in the software. We do the calculations for you, and you can filter the results to show just what you want to see. Our reporting feature is done automatically with one click.

ProjectManager is an online tool that gets real-time data to determine how accurate your planned schedule is to the actual one, so you can adjust immediately if necessary. See how it can help your project by taking this free 30-day trial.

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Critical Path Method Resources

• Critical Path Software
• Project Scheduling Software
• Gantt Chart Software
• Project Management Software
• Work Breakdown Structure (WBS) Template
• Gantt Chart Template
• Work Schedule Template
• Project Scope Template
• Top 10 Project Management Methodologies: An Overview
• 3 Free Tools for Making Network Diagrams
• Project Scheduling Guide
• The Ultimate Guide to Gantt Charts
• What Is a Work Breakdown Structure?
• PERT and CPM: Their Differences and How to Use Them Together

External Articles

• The ABCs of the Critical Path Method – Harvard Business Review
• Understanding the Basics of CPM Calculations – PMI
• What Is the Critical Path in Project Management? – Elmhurst University

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With roots dating back to the 1960s, the critical path method (CPM) is a technique used during the initial project analysis, planning, and scheduling phases of project management. The process has changed over the years since its inception, and while the modern critical path method mirrors the original in many ways, there are noticeable differences. But what is critical path in project management? 

Critical path in project management is the sequence of tasks or activities that must be completed during the execution of a project, and the critical path method is a means of mapping out these activities. In this article, we will go into greater detail when answering the question of what critical path is in project management and how to implement CPM in the 21st century.

Why It Is Important to Identify a Project’s Critical Path

Critical path is a project management term that refers to the various project tasks and activities that are the most time-consuming. Once the critical path has been identified, the individual tasks along the critical path—known collectively as critical activities—are easily prioritized and delegated as needed.

The overall project timeline ultimately depends on the critical path. Since the critical path represents the minimum amount of time needed to complete the project, it is vital to identify the critical path during the initial project planning phase.

How to Use the Critical Path Method (+ Example)

To illustrate how to use the critical path method, we’ll be using it to plan an online press conference.

Step 1: List all project tasks

Critical path project management begins with a list of all the tasks and activities, as well as the various milestones and deliverables, associated with the project at hand. For small or short-term projects, these activities can easily be listed with a simple, multi-column chart.

When planning an online press conference, for example, you might split activities into various groups: one for guests, another to cover the format of the press conference itself, yet another for logistics planning, and one more for creating an online press kit for distribution to mainstream media outlets.

Larger projects, which could involve dozens or even hundreds of separate tasks, are best managed by using CPM alongside other tools, such as a Gantt chart, to keep everything running as smoothly as possible.

Step 2: Identify dependencies and estimates

Next, take the time to identify any task dependencies within your project. These are tasks that can’t be finished until another related activity is complete. Once you’ve identified and listed dependencies, it’s useful to provide estimates of how long each individual task is expected to take. It’s okay if you don’t know exactly; a rough estimate will suffice.

If you have a list of guests you hope to see at your upcoming press conference, one of your specific tasks will involve sending out invites, either through email or traditional mail. However, you can’t start sending invitations until you’ve created them. And once created, you still need to compile the contact information for each guest.

As such, the activity of sending out invitations is dependent on the separate tasks of creating invitations and collecting contact information. Some activities, like collecting contact details, aren’t dependent on any other tasks. Other activities might have several different dependencies, so it’s important to complete this process for every activity on your list.

Read more: Understanding Task Dependency Types in Project Management

Step 3: Use a network diagram that traces dependencies

Creating a simple network diagram is a helpful way of visualizing the different project activities and their dependencies. In most cases, a diagram can be created using individual boxes to represent each task or activity. Each dependency should ultimately point to all of the tasks that can be started once it is completed. While some activities will point to several other tasks, others might point to only one.

When diagramming complicated or long-term projects, consider using different colors for each dependency. This makes it easier to track specific tasks—and their critical activities—throughout the entire project lifecycle.

Step 4: Do a forward pass

Once you have your basic diagram created, it’s time to move through your diagram with a forward pass. Not only does this ensure the validity and accuracy of your diagram, but it also makes it easy to determine the duration of the entire project. Although we already made rough estimates of the time-to-completion for each specific activity, that doesn’t really cover the project as a whole.

In order to determine the project duration, we need to introduce to new variables to the diagram:

• Early start time (ES) : This is the earliest possible time that any given task can be started.
• Early finish time (EF) : Conversely, this is the earliest possible time that any given task can be completed or finished.

Calculating the ES of each task is a straightforward process. In our project management critical path example above, the first tasks that can possibly be started are those with no dependencies. As such, they have all an ES of 0, as they can be started on day 0. To determine the EF, add the activity’s estimated duration to the ES. If task 1 takes 0.5 days to complete, for example, then the EF is 0.5.

To add these variables to our diagram, put the ES in the upper-left corner of each task box and put the EF in the upper-right corner. When calculating the EF and ES of tasks that depend on earlier tasks, make sure to add the variables from the task’s dependencies too.

Task 3, for example, has an EF of 0.5; however, it can’t be started until tasks 1 and 2 are finished. Instead of adding the two together, we simply pick the highest EF. In this case, task 3 has an EF of 1 because of its own time (0.5 days to finish) and the EFs of the previous tasks. 

Step 5: Do a backward pass

Next, complete a backward pass. Again, this process introduces two new variables to the diagram:

• Latest start time (LS) : This is the latest possible time that a task can be started without causing delays throughout the entire project.
• Latest finish time (LF) : Likewise, this is the latest possible time that a task can be finished without causing delays throughout the entire project.

To determine the LF, start by copying the final task’s EF and pasting it as the LF. As you can see in the example above, task 11 has 6.5 for both its EF and its LF.

To determine the LS, simply subtract the task’s duration from its LF. Since task 11 has a duration of 0.5 and an LF of 6.5, its LS is 6. For dependencies, use task 11’s LS as the LF of any tasks that lead directly to it. Using our critical path example, this includes tasks 3, 5, and 10. To determine the LS of these earlier tasks, simply subtract their duration from task 11’s LF. If a task points to more than one other task, use the lower LS as that task’s LF.

Step 6: Find the critical path

In order to find the project’s critical path, follow the tasks that have the same EF and LF. In our example, this has us starting on task 6 and proceeding to tasks 8, 9, 10, and 11—this is the critical path.

Remember, only critical activities can extend the project’s duration. While failing to finish task 9 on time would delay the entire project, a slight delay in task 4 or 5 wouldn’t have much effect, as long as they’re all completed by their respective LFs.

Benefits of the Critical Path Method in Project Management

Critical path aids skilled and novice project managers alike in optimizing and streamlining the entire project lifecycle. But how exactly does it help?

Prioritizing tasks

The critical path method makes it easy to prioritize and delegate tasks. Critical activities should be given the highest priority, since the project ultimately depends on those for completion. Non-critical activities can then be scheduled around the completion of these other, more important tasks.

Anticipating and avoiding bottlenecks

The CPM also helps you anticipate and avoid bottlenecks in the workflow, especially when it comes to scheduling and resource planning. Identifying the tasks that take the longest time to complete at the very beginning of your project ultimately helps you plan ahead and make the necessary accommodations before it’s too late.

Identifying slack

Sometimes known as float , slack refers to the total number of days that a task can be delayed before it affects other activities within the project. To identify slack in individual tasks, subtract the task’s EF from the LF.

Limitations of the Critical Path Method in Project Management

As useful as the CPM is, the process isn’t perfect. It has flaws, disadvantages, and limitations project managers should keep in mind.

Resource dependencies

While the critical path method makes it easy to understand individual task dependencies, it doesn’t accommodate resource dependencies. For example, assigning one person to complete two different tasks. Since the second task can’t be started until the first one is finished, there could be unexpected delays in the project duration.

Scheduling interruptions

Holidays, system updates, and PTO could all increase the overall project duration. While you certainly can’t plan for unexpected interruptions, some, like regular holidays and scheduled vacation time, should be taken into account when determining your project’s overall duration.

The CPM is best used when planning and organizing smaller projects. Large or complicated projects with hundreds or even thousands of individual tasks quickly become too bulky to be of any real use.

Manual vs Automated Critical Path Mapping

For most projects, critical path mapping can be completed manually. Our example illustrated above walks you through the steps needed to create a network diagram and critical path map without the use of software automation. For those who want to save even more time, however, there are apps and utilities that can automate much of the process.

While every software solution offers its own combination of features and functionality, some of the common elements of CPM software include:

• Drag-and-drop interface for adding tasks and dependencies
• Customizable templates for individual tasks
• Automated identification of your project’s critical path
• Collaboration amongst teammates and stakeholders
• Milestone tracking and notification
• Automated analysis and updating of start dates, due dates, and task durations

Automated CPM software is ideal for small project teams that are regularly working on large or complicated projects. It can also be used by novice PMs to guide them through the critical path method during their next project.

Critical Path Method: A Great Method for Planning a Project Timeline

The critical path method is one of the easiest and most straightforward ways of planning, analyzing, and disseminating a project timeline for project teammates, clients, and stakeholders. In project management , mapping out critical path can be implemented by novices and PM veterans alike, and it’s a proven way to streamline the typical project lifecycle while making it easier to prioritize activities and track productivity.

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The Ultimate Guide to the Critical Path Method

By Kate Eby | April 30, 2015

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In this article, you’ll learn the meaning of the critical path method, and how this method is used in project management. We’ve interviewed leading experts to help explain the key advantages of the critical path method.

Included on this page, you’ll find the six steps in the critical path method , the easiest way to find the critical path , and the best critical path software to use with step-by-step instructions.

What Is the Critical Path Method (CPM)?

CPM is a step-by-step project management technique to identify activities on the critical path. The approach breaks a project into work tasks, displays them in a flow chart, and then calculates the project duration based on estimated time frames for each. It identifies tasks that are critical, time-wise.

The text, A Guide to the Project Management Body of Knowledge (PMBOK ® Guide), an internationally recognized collection of processes and knowledge areas accepted as best practice for the project management profession, defines the critical path as “the sequence of scheduled activities that determines the duration of the project.” It is the longest sequence of tasks in a project plan that must be completed on time in order for the project to meet its deadline. If there is a delay in any task on the critical path, then your whole project will be delayed. Although many projects have only one critical path, some projects may have multiple critical paths.

Dr. Larry Bennett , a civil engineer, project manager, and author of four books, including a guide on critical path written in 1978 and titled, “ Critical Path Precedence Networks ,” explains that the critical path method helps manage projects in two different ways: “It produces a planned schedule to guide the project team, and it forms the basis for tracking project schedule performance by comparing actual with planned task progress.”

The Critical Path Method According to Two Experts 

We asked two critical path users for the best way to explain it. Here's what they had to say:

"The critical path is just a fancy way of saying 'How long does each task take before you can finish the project? Use this information to figure out the project's end date.' If a task takes longer than anticipated, the end date is pushed back. There are some tasks that don't immediately impact the project's end date that can be pushed back for some time. There are a whole bunch of calculations that go into figuring out what-ifs, forecasting, and scheduling, but that's where project management software comes in and makes everyone's lives easier. "

Rachel Burger , Capterra Construction Twitter:  @CapterraBuilder

"Some of the activities must happen in parallel. For example, if you tried to make a fried breakfast by doing one task at a time, and one after the other, things would go wrong. The plates need to be warming while other activities are going on. The toast needs to be toasting while the sausages are frying, and at the same time the bacon and sausages are under the grill. The eggs need to be fried last. A critical path analysis is a diagrammatical representation of what needs to be done and when. Timescales and costs can be applied to each activity and resource." Terence Jackson , Ph.D and CEO/Managing Partner at WEpiphany LL

“To learn about combining CPM with PERT for more comprehensive scheduling option, see this guide to combining PERT and CPM .”

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Background & History of Critical Path

Dr. Bennett is no stranger to critical path. He has applied critical path scheduling to a wide variety of projects since 1965. He has also spent 29 years on the engineering faculty at the University of Alaska Fairbanks, teaching undergraduate and graduate courses in technical management, including project management and scheduling.

In addition to his books , he has written more than 50 professional papers and articles on topics ranging from construction management to network techniques for project scheduling. 

Dr. Bennett points out that critical path has come a long way. In fact, the original critical path method was done by hand. As Dr. Bennett describes it: 

“The original critical path method used arrows to represent tasks and tied them together by connecting their beginning and end at nodes, so that proper sequencing was developed. This approach persisted for a decade, when a different method, with the same results, became popular. Professor John W. Fondahl, a professor of construction management at Stanford University, proposed in a 1961 paper that each task be represented by a node – square, circle, or oval – and the nodes be tied together with lines or arrows representing the sequence between tasks. This approach, referred to as the activity-on-node (AON) or precedence method, caught on rapidly and has supplanted the earlier activity-on-arrow (AOA) method in nearly all uses.”

How the Critical Path Method Was Created 

Using the critical path method to schedule projects began in the late 1950s, with two simultaneous, unrelated projects. The US Navy’s Fleet Ballistic Missile (Polaris) Program was behind schedule and needed help resolving the problem. The suggested solution was to divide the project into several thousand tasks, represent each task by an arrow, connect the arrows in proper sequence, estimate the duration of each task, and calculate the project duration and the degree of schedule criticality of each task. 

At about the same time, the EI DuPont de Nemours Company, an American chemical company, was experiencing delays in its plant turnarounds, a project to rearrange production facilities for different products. They, too, needed help and the proposed answer was similar to that of the Polaris Program. 

The developers of the Polaris Program’s approach called their solution the Project Evaluation and Review Technique (PERT), while the DuPont method was called Critical Path Method (CPM).  Although these methods are similar, they used different techniques for estimating task duration. 

The PERT method used three different time estimations for each task duration and calculated the probability of project completion by any given time. The DuPont approach used one time duration for each task; it was concerned not only with project completion time, but also with analyzing the extra costs that would accrue if the project duration were decreased.  

Dr. Bennett says that today, “the terms PERT and CPM are used interchangeably, both meaning any network scheduling method and PERT having lost its inclusion of three time estimates and probabilities.”

The Everyday Advantages of Critical Path

Although it originated in the late 1950s, critical path is still incredibly important to project managers today. It provides a visual representation of project activities, clearly presents the time required to complete tasks, and tracks activities so you don’t fall behind. The critical path method also reduces uncertainty because you must calculate the shortest and longest time of completion of each activity. This forces you to consider unexpected factors that may impact your tasks and reduces the likelihood that an unexpected surprise will occur during your project.

According to Dr. Bennett, the critical path method also has three main benefits for project managers:

• Identifies the Most Important Tasks:  First, it clearly identifies the tasks that you will have to closely manage. If any of the tasks on the critical path take more time than their estimated durations, start later than planned, or finish later than planned, then your whole project will be affected. 
• Helps Reduce Timelines: Secondly, “if, after the initial analysis predicts a completion time, there is interest in completing the project in a shorter time frame, it is clear which task or tasks are candidates for duration reduction,” said Dr. Bennett. When the results from a critical path method are displayed as a bar chart, like a Gantt chart, it is easy to see where the tasks fall in the overall timeframe. You can visualize the critical path activities (they are usually highlighted), as well as task durations and their sequences. This provides a new level of insight into your project’s timeline, giving you more understanding about which task durations you can modify, and which must stay the same. 
• Compares Planned with Actual: And lastly, Dr. Bennett says the critical path method can also be used to compare planned progress with actual progress. “As the project proceeds, the baseline schedule developed from the initial critical path analysis can be used to track schedule progress.  Throughout a project, a manager can identify tasks that have already been completed, the predicted remaining durations for in-progress tasks, and any planned changes to future task sequences and durations.  The result will be an updated schedule, which, when displayed against the original baseline, will provide a visual means of comparing planned with actual progress.”

Experts Share the #1 Advantage of Critical Path   

"For me, the biggest advantage of the critical path method is that it makes risk assessment easy. If I’ve got dependencies laid out and plans change, it’s very easy to say, 'Because you missed that deadline, the next deliverable is going to be late by X days, and that puts us beyond our plan by Y days.' Simple. That said, I don’t think you have to fully adopt a method like critical path to do this on projects. It’s best to adopt the parts of any method that work for your project and your team—being adaptable as a PM will help you find true success."

Brett Harned,  digital project management consultant , writer, speaker, and community builder.

Twitter:  @BrettHarned 

"Two issues that continue to plague projects are the competing priorities of cross functional team members and distractions from 'noise' on the project.  With so much activity, the critical path enables a clear, pointed view of what must happen next and 'who is on the clock' for meeting project commitments."

Robert Kelly, co-founder of  @PMChat  and managing partner of  Kelly Solutions , a project management firm. 

Twitter:  @rkelly976

"I especially like the 'unintended benefits' critical path (CP) analysis brings, including discoveries of hidden dependencies and resource conflicts. CP analysis also often leads to better prioritization and redistribution of team-members.  And CP can expose the needs / opportunities for inserting lags / leads to further improve the schedule."

Jeff Furman, PMP, author of  "The Project Management Answer Book"

Twitter:  @PMAnswerBook  

"The critical path method brings an important level of clarity to your project. It is a visual depiction of the fragility of the balance of your constraints: If one of the activities on the path gets delayed, your project gets delayed. It is also a great way to determine where to invest resources if the project has fallen behind schedule."

Cesar Abeid,  host of the Project Management for the Masses Podcast

Key Steps in the Critical Path Method

There are six steps in the critical path method: 

Step 1: Specify Each Activity

Using the work breakdown structure, you need to identify each activity (or task) involved in the project. This activity specification list should only include higher-level activities. When detailed activities are used, the critical path analysis may become too complex to manage and maintain. 

A work breakdown structure breaks down projects into manageable sections. 

The first step is to identify the main deliverables of a project. Then you can start breaking down the high-level activities into smaller chunks of work. 

You can choose how to display your work breakdown structure. Some people use a tree structure, while others use lists or tables. An outline is one of the easiest ways to represent a work breakdown structure.

Step 2: Establish Dependencies (Activity Sequence)

Some activities will depend on the completion of others. Listing the immediate predecessors of each activity will help you identify the correct order. To correctly identify activities and their precedence, ask yourself these three questions for each activity on your list from step one: 

• Which task should take place before this task happens?
• Which tasks should be finished at the same time as this task?
• Which tasks should happen right after this task?

Step 3: Draw the Network Diagram  

Once you have identified the activities and their dependencies, you can draw the critical path analysis chart (CPA), known as the network diagram. The network diagram is a visual representation of the order of your activities based on dependencies.

This critical path diagram used to be drawn by-hand, but there are now software programs that can create this diagram for you. 

Step 4: Estimate Activity Completion Time

Using past experience or the knowledge of an experienced team member, you must now estimate the time required to complete each activity. If you are managing a smaller project, you will most likely estimate time in days. If you are working with a complex project, you may have to measure time in weeks.

If you don’t feel comfortable using your best-guess estimates, you can use the 3-point estimation method, which is designed to put more weight on the most realistic timeframe. 

In three-point estimation, you must come up with three time estimates for every task, based on prior experience or best guesses. The estimation method is presented in formulas in order to calculate the time duration more accurately. 

a = the best-case estimate m = the most likely estimate b = the worst-case estimate 

These three values identify what happens in an optimal state, what is the most likely, and what happens in the worst case scenario. 

Once you’ve identified these values, you can use them in two different formulas. The first is used to find the Weighted Average, which puts more weight on the “Most Likely” value. The formula is as below. E stands for Estimate, and the 4 and 6 represent the standard method to place more weight on the most realistic value. 

E = (a + 4m + b) / 6

The second way of using these values is known as Triangular Distribution. The main difference is that this method doesn’t put more weight on the “Most Likely” value. The formula is as below. E stands for Estimate, and the 3 represents the standard method.

E = (a + m + b)/3

Step 5: Identify the Critical Path   

There are two ways you can now identify the critical path. You can eyeball your network diagram and simply identify the longest path throughout the network -- the longest sequence of activities on the path. Be sure to look for the longest path in terms of longest duration in days, not the path with the most boxes or nodes. 

You can also identify critical activities with the Forward Pass/Backward Pass technique, identifying the earliest start and finish times, and the latest start and finish times for each activity. 

If you have multiple critical paths, you will run into network sensitivity. A project schedule is considered sensitive if the critical path is likely to change once the project begins. The more critical paths in a project, the higher the probability of a change in schedule. 

Step 6: Update the Critical Path Diagram to Show Progress 

As the project progresses, you will learn the actual activity completion times. The network diagram can then be updated to include this information (rather than continuing to use estimations).

By updating the network diagram as new information emerges, you may recalculate a different critical path. You will also have a more realistic view of the project completion due date and will be able to tell if you are on track or falling behind.

Other Scenarios in the Critical Path Method

One of the biggest benefits of the critical path method is identifying the crucial tasks that, if missed, will impact your project’s completion date. It will also provide visibility into your project’s status, allowing you to see if you are on track. 

Shortening Your Schedule

As you’re going through the critical path method, you may find that you want to intentionally shorten the duration of your project or that you need to compress your project schedule in order to meet the deadline. There are two ways to do this: fast tracking or crashing.

Fast Tracking 

In fast tracking, you look at the critical path and decide which activities can be done parallel to each other, to move the project along faster. You only need to review the activities on the critical path because all the other activities have float (if you shorten the duration of those activities, you’re only giving them more float). 

While fast tracking reduces your project timeframe, it also involves risk because you are performing parallel activities that were originally planned to be performed in sequence. 

Crash Duration 

Crash duration, or crashing, refers to the shortest possible time for which an activity can be scheduled. This happens by adding more resources to completing that certain activity. However, crashing the critical path results in lower quality of work because the goal in crash duration is speed.

Managing Resource Constraints 

As you manage your project, you may also run into resource constraint issues that could change the critical path. If you try to schedule certain activities at the same time, you may find that you need more people than are available. As a result, those activities will need to be rescheduled. Resource leveling is the process of resolving these conflicts. 

Resource Leveling and Expansion 

With resource leveling, you can resolve conflicts over allocating resources. A resource-leveled schedule may include delays due from resource bottlenecks (a resource being unavailable at the necessary time). 

Resource leveling may also result in a previously shorter path becoming the longest or most “resource critical” path. This happens when the tasks on the critical path are affected by resource constraints. 

A similar concept is called the critical chain, which protects activity and project durations from unexpected delays due to resource constraints. 

Assessing the Final Project

These scenarios demonstrate all the unexpected changes that can occur when managing a project, and how they can affect the critical path. While things are always subject to change, the good news is that you can measure the variance from your original project schedule and track how it impacted your final project. 

Flexibility and Assessing Delays

A schedule created from the critical path method naturally involves a lot of fluctuation because you have to use best-guess estimates to calculate time. If one mistake is made in activity completion time, your whole critical path schedule could change. Or, you may need to purposefully delay project activities due to resource constraints. 

Sorting out these delays and determining what caused them can help you avoid similar issues in the future. An important part of your post-project plan is the As Built Critical Path, which analyzes the specific causes and impacts of changes between the planned schedule and actual schedule implemented. The As-Built Critical Path is a schedule that shows the dates that the activities actually occurred and allocates time by determining the responsibility for the delays on the critical path. 

Critical Path Software

When the critical path method was first developed, you had to identify the critical path by hand, drawing the network diagram with “nodes” to present the stages of a project and connecting the nodes with arrows or “arcs.” 

However, drawing nodes, tables, and arrows can be a time-consuming, difficult task, especially when things are constantly changing at the beginning of a project.

Rather than relying on hand-draw diagrams, there are a number of project management software programs available today that will do the work for you and identify the critical path with the click of a button.

Here are two different tools with critical path features:

Find the Critical Path with Microsoft Project

You can display the critical path in the Gantt chart view of Microsoft Project.

First, you must enter all your tasks, their start and end dates, the duration of each task, and identify the predecessors. Then, you can adjust the view of your MS Project file to display the critical path.

• Click View > Gantt Chart.
• Click Format and then select the Critical Tasks check box.  

Tasks on the critical path now have red Gantt bars.

Identify Critical Path in Other Views

You can see the critical path in any task view by highlighting it.

• Click the View tab and select a view from the Task Views group.
• Staying within the View tab, click Critical from the Highlight list. The critical path shows up in yellow.
• To see only the tasks on the critical path, click the Filter arrow and select Critical .  

In a network diagram, tasks on the critical path automatically show up in red. No highlighting is needed.

See the Critical Path in a Master Project

Entire subprojects can be on the critical path when you’re managing a master project. To identify subprojects on the critical path, you can adjust Microsoft Project to treat the subprojects like summary tasks.

• Click File > Options .
• Select Schedule and then scroll down to the Calculation options for this project .  

Make sure the Inserted projects are calculated like summary tasks box is selected.

Change the Tasks on the Critical Path

Critical tasks typically have no slack. However, you can tell Microsoft Project to include tasks with one or more days of slack on the critical path, so you can identify any potential problems that may arise.

• Click Advanced , then scroll down to the Calculation options for this project area.
• Add a number to the Tasks are critical if slack is less than or equal to box.  

Identify the Critical Path in Seconds with Smartsheet

Smartsheet, a work management and collaboration tool in a spreadsheet layout, offers a pre-formatted Gantt chart template  to make it even easier to find the critical path.

With this pre-made Gantt chart template, complete with sections, sub-tasks, and sub-sub-tasks already formatted, all you need to do is enter your own project planning information. A Gantt chart will automatically be made for you, and with the click of a button, you can identify the critical path on the Gantt chart.

Here’s how to find the critical path in Smartsheet, using a Gantt chart template:

1. Choose a Gantt Chart Template

• Go to Smartsheet.com and login to your account (or start a free 30 day trial ).
• From the Home screen, click Create New and choose Browse Templates .
• Type “dependencies” in the Search Templates box and click the magnifying glass icon.
• Select the Basic Project with Gantt & Dependencies and click on the blue Use Template in the upper-right corner.
• Name your template, choose where to save it, and click the OK button.  

2. List Your Task Information

A pre-made, formatted template will open with sample content filled in for reference. This section is where you add your activities, or tasks, from your work breakdown structure. This is also where you can show the hierarchy, or relationship, between tasks.

The yellow cells at the top are there simply for instructional reference. To delete them, right-click on each yellow box and select Delete Row .

• Add your tasks under the Task Name column.
• Use the cells named Section 1, Section 2, and Section 3 to establish hierarchy (for more information on hierarchies, click here ).
• If you need to delete a row, right-click on the cell in the row you’d like to delete and select Delete Row .  

On the left side of each row, you can attach files directly to a task or start comments with a colleague about a task, adding more context to your project.

3. Provide Start and End Dates

Add start and end dates for each task. If you click and drag either end of a green task bar on the right in the Gantt view, Smartsheet will automatically change the matching dates in the task table.

• Select a cell in the Start Date or End Date column.
• Click on the calendar icon and choose a date.  

You can also manually enter a date in the cell. Smartsheet will automatically calculate the duration of each task for you.

4. Add % Complete and Assigned To Information

The % Complete and Assigned To columns provide more context around your project. In the Gantt view on the right side, you can quickly see how much of a task has been completed by the length of the thin grey bars inside the task bars.

The Assigned To column allows you to assign the task to a particular team member, providing visibility into who is doing what.

• In the % Complete column, enter the percentage of work complete for that task. Enter a whole number and Smartsheet will auto-fill the percentage sign.
• In the Assigned To column, choose a name from the drop-down menu or manually enter a new name.

5. Establish Predecessors

Predecessors are used to create dependencies between tasks (identifying which tasks need to happen before or after another task).

• On the far-left of the sheet, each row is assigned a number. In the Predecessor column, enter the row number that represents the row of the preceding task. This will create a link from the current row (the dependent task) to the specified row (the predecessor task).
• Enter the row numbers of all other predecessors in the Predecessor column.  

You can also create predecessor dependencies from the Gantt chart on the right. Drag the bottom, right-corner of a Gantt bar down to the Gantt bar of the task that should follow it. The Predecessor column will be automatically updated.

6. Identify the Critical Path

Now that you have created a Gantt chart in Smartsheet, you can identify the critical path on the Gantt chart with the click of a button.

• On the right side of the screen, where your Gantt chart is displayed, click the far-right button that depicts a critical path (the two red Gantt bars).
• On the Gantt chart, the tasks that are on the critical path will be outlined in red.  

How to Import a Microsoft Project File (.MPP) into Smartsheet

Smartsheet works with Microsoft Project, so if you already have your project planning information stored in Microsoft Project, you can easily import that directly to Smartsheet.

• Click the Home tab and click the grey Import button.
• Choose the Import MS Project File .  

• Click Select, choose the file you would like to import, and click Open .
• Click Continue and an Import Settings form appears. Select the row in the form that contains your column headers (it will probably be the first row) and click Import .
• The imported file will appear as a new sheet within Smartsheet. Click on the sheet name to open it.

Studying for the PMP® Exam? Here’s What You Need to Know about the Critical Path Method

To earn your Project Management Professional (PMP) ® credential, you need to pass the PMP exam, a 200-question, multiple choice test offered by the Project Management Institute (PMI).

Critical path is an important part of the PMP Exam and there will certainly be questions about it on the test. You’ll need to be able to draw a network diagram, identify the critical path, use the Forward Pass/Backward Pass technique, and calculate slack.

Here is an overview of the most important things to know about the critical path method to help you pass the PMP exam:

How to Draw a Network Diagram

On the PMP Exam, you will be asked to draw a network diagram. The exam will list all the activities in a project and will tell you when the activities can start. With that information, you’ll be asked to identify the critical path and its duration.

To explain how to draw a network diagram, Bennett has created a sample eight-task project:

• Design Tank Project (10 days) can start right away.
• Construct Tank Foundation (25 days) and Select Tank Supplier (8 days) can start as soon as Design Tank Project is finished.
• Manufacture Tank Components (10 days) can start as soon as Select Tank Supplier is finished.
• Deliver Tank to Jobsite (4 days) can start as soon as Manufacture Tank Components is finished.
• Prepare Installation Drawings (3 days) can start as soon as Select Tank Supplier is finished.
• Assemble Tank (15 days) can start as soon as Deliver Tank to Jobsite, Prepare Installation Drawings and Construct Tank Foundation are all finished.
• Test & Commission Tank (4 days) can start as soon as Assemble Tank is finished.
• After Test & Commission Tank is finished, the project is complete.  

To answer the question, you’ll need to draw a network diagram.

Here’s how:

• Draw a box and label it as your first activity (Design Tank Project). In the box, make sure to write the duration in days (in this case, it is 10 days).
• Begin your diagram by drawing the relationship between Design Tank Project, and Construct Tank Foundation and Select Tank Supplier. You can do this by drawing a box for the other activities, and drawing arrows to these boxes from Design Tank Project.
• Continue drawing boxes to represent activities, and arrows to represent when an activity can begin.  

After you have drawn the network diagram, you will be able to find the critical path. Remember: the critical path is the longest duration path throughout the network in days, not the path with the most boxes.

In this example, the critical path is Design Tank Project, Construct Tank Foundation, Assemble Tank, and Test & Commission Tank, with a total duration of 54 days.

You can identify the critical path by eyeballing the diagram to find the longest duration in days, or you could use the Forward Pass/Backward Pass Technique outlined in the next section.

How to Use the Forward Pass/Backward Pass Technique

The Forward Pass/Backward Pass technique is another way to find the critical path. It is best used when you have multiple branches, or multiple entry points, for an activity. 

You may also need to use the Forward Pass/Backward Pass technique if you are asked to identify the earliest start or finish times, or latest start or finish times, for an activity. Or, to find the slack (or float) for each activity.

Before you start using the Forward Pass/Backward Pass technique, here are some terms that you first need to understand:

• Earliest start time (ES): The earliest time an activity can start once the previous dependent activities are completed.
• Earliest finish time (EF): The earliest start time for the activity plus the time required to complete the activity (the earliest an activity can be completed).
• Latest finish time (LF): The latest time an activity can be completed without delaying the entire project.
• Latest start time (LS): The latest finish time minus the time required to complete the activity.

As you run the Forward Pass/Backward Pass technique through your network diagram, arrange each value according to the following legend (SL stands for slack, which we’ll cover in the next section).

How to Do the Forward Pass: Finding the Earliest Start Time and Finish Time

There are two formulas in the Forward Pass/Backward Pass technique. The first is the Forward Pass formula for you to use as you move from beginning to end in your network diagram (from your first activity to your last). This formula will find the earliest start time (ES) and the earliest finish time (EF) for each activity.

To start the Forward Pass, make the ES of the first task zero. For all other tasks, the ES is the same as its immediate predecessor’s EF.

Use this formula to calculate EF:

EF = ES + Duration

So, for Design Tank Project, the ES is zero and, the EF is 10 (10+ duration of 0). We also know that the ES for Select Tank Supplier is 10 and the EF is 18 (10 + duration of 8). Continue like this throughout the network diagram.

How to Do the Backward Pass: Finding the Latest Start Time and Finish Time

The second formula is for Backward Pass, when you are moving from the last activity to the first activity (you are moving backwards). This formula will find the latest start time (LS) and latest finish time (LF) for each activity.

To start the Backward Pass, make the last activities LF the same as its EF. For all other tasks, the LF is the same as its immediate predecessor’s LS.

Use this formula to calculate LS:

LS = LF - Duration

For the Test & Commission Tank, the LF is 54 and, the LS is 50 (54 - duration of 4). For Assemble Tank, the LF is also 50 and, the LS is 35 (50 - duration of 15 days). Continue this formula throughout the network diagram.

To check that you’ve done Backward Pass correctly, the first activity (Activity A) should have an LS (latest start time) of 0.

Here’s the completed Forward Pass/Backward Pass technique:

Two Rules to Remember for Forward Pass/Backward Pass

During the Forward Pass, if you find activities that join (multiple activities that flow into one activity), you must run the Forward Pass formula for each entry point and use the highest value from the formulas.

During the Backward Pass, if you have activities that join, you must run the formula for each entry point and use the lowest value.

How to Calculate Float or Slack on the PMP Exam

Now that you have calculated ES and LS for each activity, you can find the float (or slack).

The slack time, also known as float time, for an activity is the time between the earliest and latest start time. Critical activities, activities on the critical path, will always have zero slack.

There are two formulas to calculate slack based on the values you identified in the Forward Pass/Backward Pass technique.

Slack = LF - EF

Slack = LS - ES

You will have to use this process if you are asked to identify an activity’s slack on the PMP exam. Or, if you’re not sure which activities are on the critical path, you could find the slack of each activity, knowing that activities on the critical path always have zero slack.

The final figure below shows the slack values for each task. You can see that the four tasks on the critical path have zero slack -- Design Tank Project, Construct Tank Foundation, Assemble Tank, and Test & Commission Tank.

Key Critical Path Terms for the PMP Exam

Here are the most important terms related to the critical path method that you should understand before taking the PMP exam.

• Critical path method (CPM): The critical path method is a step-by-step project management technique for process planning that identifies critical and noncritical tasks, preventing timeframe problems and process bottlenecks.
• Critical Path DRAG (Devaux’s Removed Activity Gauge): The amount of time that an activity on the critical path is adding to the project’s duration. Or, alternatively, the amount of time the project completion date would be reduced by decreasing a critical path activity’s duration to zero.
• Criticality Index: Used in risk analysis, the Criticality Index shows how often a particular task was on the critical path during analysis. Tasks with a high Criticality Index are more likely to cause delay to the project since they’re more likely to be on the critical path.
• Earliest start time: The earliest time an activity can start once the previous dependent activities are completed.
• Earliest finish time: The earliest start time for the activity plus the time required to complete the activity.
• Latest finish time: The latest time an activity can be completed without delaying the entire project.
• Latest start time: The latest finish time minus the time required to complete the activity.
• Total float: The amount of time an activity can be delayed from its early start date without delaying the entire project.
• Free float: The amount of time an activity can be delayed without delaying the early start date of a successor activity.
• Forward pass: The process to determine the early start or early finish times for activities in the critical path method.
• Backward pass: The process to determine the late start or late finish times for activities in the critical path method.
• Network diagram: A schematic display of the relationships between project activities, always drawn from left to right to reflect the order of the project.
• Network analysis: The process of breaking down a complex project into components (activities, durations, etc) and plotting them to show their interdependencies and interrelationships.

The Easiest Way to Find the Critical Path

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*The Project Management Professional (PMP) and PMBOK Guide are registered marks of the Project Management Institute, Inc. ​

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What is the critical path method? Complete guide with examples

“It depends” is a phrase sometimes referred to as the classic product management answer — and it is! While we all would love a simple answer to many of life’s questions, there are often many factors at play which means, well, it depends!

One factor product managers have to consider in their answers is dependencies. These activities might not be in the direct control of the product team but are required as part of the product development effort for success. No matter how best companies structure themselves to minimize dependencies, often they still exist. Finding out which ones matter and which impact timelines the most can be challenging. That is where the critical path method (CPM) can help.

What is the critical path method (CPM)?

The critical path method (CPM) is a widely-used project management technique that helps plan and schedule complex projects. It is used to identify the critical path of a project, aka the sequence of activities that determines the minimum completion time of the project.

What does “critical path” mean?

A critical path is a sequence of “critical” activities in a project that must be completed on time for the project to be completed on schedule. These “critical” activities will also help you to determine the minimum completion time for the project.

For example, if you’re building a house, the critical path might include activities like laying the foundations, building the walls, and installing the roof. All of these are needed to build a house and if any of these activities fall behind schedule, the entire project will be delayed.

What is the critical path method in project management?

The critical path method (CPM) is a tool used to plan and schedule complicated projects. It is based on identifying the critical path of a project and analyzing it to find the minimum completion time for the project.

The method considers the dependencies between different activities and the amount of time required to complete each activity. By understanding the critical path and the amount of “float” or “slack” time available in the schedule, project managers can better plan and control their projects.

A brief history of the critical path method

The Critical Path Method was first developed by Morgan R. Walker of DuPont and James E. Kelley Jr. of Remington Rand in the late 1950s . They were looking for a way to manage the complicated construction projects they were undertaking, so developed the CPM as a tool to help with this.

The method quickly gained popularity and was soon adopted by many companies and industries. Today, the CPM is widely used in project management and is considered an essential tool for planning and scheduling complicated projects.

Key terms associated with the critical path method

• Earliest start time (EST) : the earliest time an activity can start, taking into account the preceding activities and their durations
• Latest start time (LST) : the latest time an activity can start without delaying the project
• Earliest finish time (EFT) : the earliest time an activity can be completed, taking into account the preceding activities and their durations
• Latest finish time (LFT) : the latest time an activity can be completed without delaying the project
• Float or slack : the amount of time that an activity can be delayed without delaying the project
• Critical path : the sequence of activities that determines the minimum completion time for the project

How to find the critical path of a project

You can find the critical path of a project by following these steps:

• List all of the activities in the project, including their durations and dependencies
• Draw a network diagram to represent the dependencies between the activities
• Determine the earliest start time (EST) and earliest finish time (EFT) for each activity by working forwards through the network diagram
• Determine the latest start time (LST) and latest finish time (LFT) for each activity by working backward through the network diagram
• Identify the activities that have zero float (LST = EST) or negative float (LST < EST). These activities are on the critical path

When to use the critical path method

The critical path method (CPM) is an effective tool for planning and scheduling complicated projects. It is best for when the project has a large number of activities, many of which are interdependent. It’s useful when there are a lot of dependencies between different tasks and activities that must be taken into account to schedule the project effectively.

The method can also be useful when there is a desire to accurately predict the completion date for the project, or if resources need to be allocated optimally.

The CPM is generally less effective for simple projects with only a few activities, or projects where the activities are not closely dependent on each other. The method is also not a good fit for projects that have low predictability and require flexibility since the critical path is based on predetermined dependencies and durations.

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The critical path method for product managers

So, if your product development is operating in a project set up and has a high number of dependencies, this tool could be useful for you and your team to better understand your dependencies and the relationship between them.

Also, while many plans are incorrect the moment you finish them, the act of planning can be useful — more useful than the plan itself. Planning gives you space to think about all the factors that will go into your successful product feature or launch and fosters communication between interested parties.

However, CPM is not suitable where there is low predictability or if flexibility is necessary. I have yet to come across a team developing software that can accurately predict how long even the smallest task takes, or that doesn’t have to deal with changing requirements. I believe most product teams operate in a complex environment, over a complicated environment where the CPM is most effective.

The Cynefin framework gives us a way of identifying the structures we operate in and identifies five domains. It covers two of the domains I reference above — the complicated and the complex.

In the complicated domain, things are more predictable and known. You can rely on best practices. Perhaps, if you are developing a product at the later end of the product lifecycle your team is in a complicated domain. However, the complex domain is novel and experimentation is necessary to work out what will be successful. If you are developing anything new you are more likely to fit into this domain and find CPM ineffective.

The critical path method (CPM) is a tool to plan and schedule complicated projects. It is based on identifying the critical path of a project and analyzing it to find the minimum completion time for the project.

For product managers, the analysis of what makes the critical path and consequential planning can be very helpful to foster communication and bring about a shared understanding of the activities needed for success.

However, as many teams operate in a complex, uncertain environment that requires flexibility, the CPM is unlikely to provide the answer you are probably looking for — when will it be done.

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What is the critical path method?

table of contents

Introduction to the critical path method (cpm).

In project management, staying on top of timelines and tasks can be as complex as untangling a ball of yarn. Thankfully, there's a trusted technique to help us out: the Critical Path Method (CPM). This proven approach optimizes planning , streamlines workflow, and helps coordinate a project's diverse components. Buckle up as we take you on a deep dive into the Critical Path Method.

Understanding the Critical Path Method

Definition of critical path method.

The Critical Path Method, or CPM, is a project modeling technique that helps project managers plan, schedule, and execute their projects effectively. It pinpoints the crucial tasks — the ones that, if delayed, would push back the project's entire timeline.

Historical background and development of CPM

Born out of the need to streamline complex projects during the 1950s, CPM was first employed by DuPont Corporation and Remington Rand Univac for plant maintenance and construction projects. This method proved invaluable for managing multifaceted projects with interdependent activities, and it's been a staple in project management ever since.

Essential components of CPM

At its core, CPM operates using three essential elements: tasks, durations, and dependencies. Tasks are the individual activities necessary to complete the project. Durations are the time required to complete each task. And dependencies describe the sequential relationships between tasks.

Explanation of terms related to CPM

For a deeper grasp of CPM, let's delve into its key terms. 'Float' or 'slack' is how long you can delay a task without waiting for the project. 'Early start' and 'early finish' times are the earliest times a task can begin or end without delaying the project, and 'late start' and 'late finish' times are the latest they can start or end without causing delays.

Working of the Critical Path Method

Explanation of the step-by-step process of cpm.

The essence of CPM is in its systematic approach, which is outlined in these steps:

Breaking down the project into tasks: This process, also known as Work Breakdown Structure (WBS) , is crucial in understanding the task hierarchy and organization. Each task should be manageable and distinct with clear boundaries.

Establishing dependencies between tasks: Not all tasks are created equal. Some cannot begin until others are completed - these are known as dependent or sequential tasks. Conversely, some tasks can be undertaken simultaneously - these are parallel or concurrent tasks. This step demands a comprehensive understanding of task interrelationships.

Estimating task duration: An essential aspect of CPM is accurately estimating how long each task will take. This relies heavily on experience, historical data, and sometimes educated guesses. It's wise to factor in some buffer time for unexpected delays.

Creating the network diagram: This visual representation of tasks and their dependencies allows project managers to see the flow of activities and the critical path. This diagram can take the form of a Gantt chart or a flowchart. The nodes (representing tasks) are connected by arrows (indicating sequence).

Identifying the critical path: The critical path is the longest-duration path through the network diagram and indicates the shortest time the project can be completed. Any delay in tasks on this path directly impacts the project completion date.

Visual depiction of CPM with sample network diagrams

Network diagrams create a visual narrative of the project flow. The nodes (or circles) in the network diagram represent activities, and arrows depict the sequence of tasks. The path from the start to the end that takes the longest time is the project's critical path. Any changes in these tasks' duration will alter the project's timeline.

Importance of identifying the longest sequence of tasks - The critical path

The critical path is essential for project managers because it indicates the tasks directly impacting the project's duration. Managing these critical tasks efficiently ensures the project stays on track and any potential delays are mitigated promptly.

Application and benefits of the Critical Path Method

Various sectors where cpm is used.

CPM isn't restricted to any particular industry. Its practical applications span various sectors like construction (for scheduling stages of a building project), manufacturing (for managing production steps), software development (to navigate coding, testing, and debugging phases), and event planning (for coordinating many event preparations).

Real-world examples of CPM application

To illustrate CPM's real-world application, consider the Apollo project by NASA. The CPM managed the thousands of interrelated tasks required to land a man on the moon. The Sydney Opera House project used CPM to manage its complex building process in the construction sector.

The impact of CPM on project efficiency

By identifying the longest stretch of dependent activities, CPM helps maintain project efficiency. It minimizes idle resources, ensures time is well-managed, and guarantees all project activities are aligned toward the end goal. It also allows project managers to prioritize resources and tasks, further boosting efficiency.

Benefits of using CPM in project management

CPM enables better control over project timelines, early identification of potential delays, and more efficient resource allocation. It also improves risk management by identifying the most crucial tasks, enabling focused and strategic contingency planning.

Challenges and limitations of the Critical Path Method

Recognizing the inherent uncertainty in task durations.

One significant challenge in CPM is the inherent uncertainty in task duration estimates. These estimates often rely on past data and personal judgment, making them vulnerable to inaccuracies. Real-life problems, unexpected changes, and other uncertainties can alter task durations, affecting the critical path.

Challenges related to resource allocation

While CPM is excellent for time management, it does not inherently consider resource allocation. Projects often have limited resources, and multiple critical tasks may require the same resources simultaneously. Project managers often need to adjust schedules or resources to manage such conflicts.

Complexity and time involved in creating and updating the CPM

Creating and updating a CPM diagram can be complex, especially for larger projects with many interrelated tasks. Keeping the diagram updated requires consistent effort, making it a time-consuming process.

Limitations of CPM

CPM assumes that the project environment and task durations are stable, which may not always be true. Other methods, like the Program Evaluation and Review Technique (PERT), might be more suitable for highly uncertain or agile environments.

Comparative Analysis: Critical Path Method and other Project Management Techniques

A. Comparison with the Program Evaluation and Review Technique (PERT)

While both CPM and PERT help manage complex projects, they handle task duration differently. PERT uses three-time estimates (optimistic, most likely, and pessimistic) to account for uncertainty, making it ideal for projects where task duration variability is high.

B. Comparison with the Gantt Chart method

Gantt charts provide a visual representation of the project schedule and are excellent for tracking project progress. However, they don't easily show task dependencies and the critical path, making them less suitable for managing task sequences in complex projects.

C. Criteria to decide which project management tool to use

The choice between CPM, PERT, Gantt, or any other project management tool depends on the nature of your project. For deterministic, well-structured projects, CPM works well. For projects with high uncertainty in task duration, PERT could be more suitable. Gantt charts, on the other hand, are great for presenting project schedules and progress to stakeholders. It's also essential to consider the team's familiarity and comfort with the chosen tool.

Using a Critical Path Method Tool is an indispensable part of a project manager's toolkit, providing a roadmap to keep projects on track. While it has limitations and may not suit every project, its benefits in planning, coordination, and efficiency are undeniable. Mastering techniques like CPM will help navigate the complex landscapes of today's project worlds as project management continues to evolve.

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Breaking down the critical path method (cpm) in project management.

July 31, 2023

In the world of complex projects, delivering on time is a must.

After all, missing deadlines is like wearing a neon sign that says unreliable to clients. To ensure success, adopting a realistic and meticulous planning approach is crucial. 

You may not have superhuman capabilities, but you have the critical path method. 

This powerful technique can help you supercharge your project management by precisely analyzing task dependencies and critical sequences! 💥

This article explains the critical path method, its benefits, use cases, and main elements. It’ll also provide step-by-step guidelines and suggest some helpful project management software to make implementing the critical path method easier, even for beginners.

Critical path medod vs. PERT

Benefits of using the critical path method in project management, when to use the critical path method, project activities, task dependencies, network critical path diagram, formulas and metrics, step 1: create a list of tasks, step 2: define task dependencies, step 3: visualize, step 4: estimate the task duration, step 5: identify the critical path, step 6: execute and revise, example of critical path analysis.

What Is the Critical Path Method? 

The critical path method is a series or sequence of must-do tasks determining the project’s overall timeline. We call such tasks critical activities, and they’re essential for the successful and timely execution of a project. ⏲️

The critical path method , also known as critical path analysis (CPA), is a technique project managers use to form accurate schedules across the entire project. They do so by identifying critical dependent tasks by calculating their duration using a specialized formula (or critical path algorithm).

They also often use Gantt charts or other diagrams to visualize and better understand the project timeline . Project managers use this to get a complete bird’s-eye view of the entire project and its dependent tasks to make better decisions.

The method was developed in the 1950s by Remington Rand’s James E. Kelley and DuPont’s Morgan R. Walker, who were looking to cut costs associated with inefficient scheduling. The pair also invented the Program Evaluation and Review Technique (PERT), a similar method often used alongside the critical path method.

CPM and PERT are both project management methodologies for planning and scheduling. Unlike CPM, which is a deterministic model, PERT is probabilistic, meaning it considers a range of possible durations for each task to provide a more flexible timeline estimation.

To delve deeper into their differences, refer to the table below:

Project managers will find many benefits to using the critical path method, including:

• Accurate estimation : Thanks to the critical path method, you can make predictions, set realistic expectations, and successfully plan the rest of the project
• Effective planning : Easily create a well-structured, realistic, and adaptable critical path project schedule and prevent major setbacks toward project completion
• Task prioritization : Critical path method helps you identify critical tasks that need to be at the top of your priority list and the most logical order of completing them
• Resource optimization : Once you know what must be done, by when, and in which order, you can effectively assign work and allocate other resources
• Improved communication : With a defined, visualized schedule, it’s easier to ensure everyone’s on the same page, which contributes to a smoother workflow

Critical path analysis should happen at the beginning of the project lifecycle . It’s typically performed in the planning stage before scheduling. In some cases, project managers carry this out even earlier and included it in the project proposal .

Industries that deal with complex projects , such as construction , engineering, and event planning, are the ones that benefit most from the critical path method. Besides projects involving many moving parts, the critical path method can also be helpful when it comes to time- or resource-constrained projects . 🚨

Key Components of the Critical Path Method

Before we start exploring CPM step-by-step, let’s learn its main concepts and their meaning. Think of the next section as your critical path method glossary ! 📖

In CPM, activities can be critical or non-critical . Critical activities are those you identify as important and include in the critical path. Non-critical project activities are all other tasks. They are less time-sensitive or essential, giving you more flexibility in scheduling.

Here’s a simplified example: If your project is to build a house, laying the foundation and installing the roof would be considered critical activities, while interior decoration would fall into the non-critical category. 🏠

Activities have their relationships, i.e., dependencies. What that means is that they have to happen in a specific order . For instance, some dependent tasks have to finish before others can start, or they have to start simultaneously. 

To continue with our house-building example—you can’t start furnishing a room until you’ve finished the flooring and the wall paint has fully dried. 🛋️

The network critical path diagram is a flowchart for visualizing your project’s timeline and task dependencies . It consists of nodes, which are usually represented with rectangles or circles, and connectors, i.e., arrows. 

Visualizing the structure of activities this way makes it easier to understand and identify the critical activities. A critical path diagram sometimes highlights areas in different colors to stand out from the non-critical task sequences.

You can also use Gantt charts and PERT charts to visualize your project timeline and critical paths, but more on that in the how-to section! 👀

The critical path method consists of a series of calculations to determine the duration of tasks and the critical path. The primary metrics are:

• Earliest start time (ES) : The earliest possible date you can start an activity considering the dependencies
• Earliest finish time (EF) : The earliest possible date you can complete an activity considering its ES and duration
• Latest start time (LS) : The last possible date you can start an activity before causing a significant project delay
• Latest finish time (LF) : The latest possible date you can complete a task based on its LF and duration
• Task duration (t) : The total amount of time it takes to complete an activity

The critical path formula has two parts, which we’ll explain below.

Forward pass

We use the forward pass to calculate the ES and EF . 

The ES of the first activity on any path will always be 1 since it indicates the start, i.e., the first day of your project. 

The ES of all other activities equals the earliest endpoint of the preceding activity plus 1:

ES = EF of preceding activity + 1

The EF equals the sum of ES and the duration of the activity minus 1:

EF = ES + t – 1

Backward pass

With the backward pass, we calculate the LS and LF .

The LF of the last activity on any path will always be the same, as it indicates the end, i.e., the last day of the project. 

The LS of an activity equals the difference between LF and the duration of the task plus 1:

LS = LF – t + 1

The LF of an activity equals the LS of the succeeding activity minus 1:

LF = LS of succeeding activity – 1

Float/Slack

The float or slack represents how long a non-critical task can be delayed without affecting the entire project timeline. Critical tasks don’t allow delays, so their float score is automatically 0.

There are two types of float:

• Total float : The amount of delay that doesn’t affect the project completion date (LS or LF – ES or EF)
• Free float : The amount of delay that doesn’t affect the start date of the succeeding task (ES of succeeding activity – EF of current activity)

How To Calculate the Critical Path in Project Management

Now that you’ve mastered all the elements of the critical path method, it’s time to put your knowledge to the test. In this section, we’ll show you how to calculate your project’s critical path in six steps. 🧮

Pro tip : If you opt for a project management tool like ClickUp , you can spare yourself from the manual and repetitive work. Instead of starting from scratch, use the pre-built ClickUp Critical Pathway Analysis Template .

With numerous task management features and intuitive Gantt charts, this tool makes CPM more accessible and streamlined! 🙌

The first thing you should do is determine the project scope . Collect all your activities in one place and define your goals, budget, and deadline. 

ClickUp’s List View provides you with the perfect framework for that. It’s a spreadsheet in which you can list all the tasks, subtasks, and relevant information about them in custom fields, such as:

• Start and due dates
• Responsible department
• Accompanying documents

Feel free to add other custom fields to aid your project planning. You have over 20 field types at your disposal, including dropdown, checkbox, rating, and progress bar. 

Besides listing tasks, you can also assign them, attach files, and lead discussions with your team in the comments. 

Not a fan of spreadsheets and lists? Project managers can do everything in a Kanban-style ClickUp Board view as well to stay on top of the project schedule, uncover resource constraints, and see actual progress toward project completion. 

Accurate identification of dependencies is crucial for successful time estimation and planning. Discuss with your team and use your previous experience to figure out the most logical order of tasks . 

To define task relationships in ClickUp, right-click on a task and select the Dependencies option. You can choose between three types:

• Waiting on : Tasks that must be completed before the selected task
• Blocking : Tasks that can’t start before the selected task has been completed
• Related : Tasks that are related but not dependent on the selected task

Defining relationships is even easier in Gantt view. You only need to select the point on either side of the taskbar and drag it over to the corresponding point on the other task. 

The best part is—this view allows you to automatically reschedule dependent tasks. To activate it, open the Show dropdown menu and toggle on the Reschedule Dependencies option.

Use a network diagram, work breakdown structure (WBS) , PERT chart , or any other visualization method to make the complex project task structure more comprehensible. Draw the flowchart and arrange tasks based on their chronological order and dependencies .

You can use pen and paper, a text editing or drawing program, or project management software like ClickUp.

ClickUp’s Whiteboard View lets you brainstorm and collaborate with your team on decisions. You can create good-looking WBS or PERT charts in no time. Use shapes and connectors to create the structure. Add additional elements like images and docs to make the diagram more informative.

As per usual, you can start with a template to save time. ClickUp has many ready-made frameworks for you to use, such as this universal ClickUp PERT Chart Template or the ClickUp Simple PERT Chart Template .

Although different in terms of structure, Gantt charts are also a convenient way to envision the sequence of tasks in a project and estimate their duration. In ClickUp, Gantt charts are interactive and adaptable. They enable you to draw the roadmap and schedule tasks simultaneously in only a few clicks. 

The next step is to define the t for each task, i.e., how many days it will take to complete it. Estimate based on your experience, historical data, and industry standards . Consult others, particularly experts, to gain multiple perspectives and make the most accurate predictions.

Input the information in the designated fields in List View or update it directly in Gantt view by resizing the taskbars. 

Using the formulas we shared earlier, calculate the ES, LS, EF, LF, and slack . Begin with the first task, which has a start time of 1, then define the EF and LF based on its duration. Repeat the same for all other tasks. 

The longest sequence of critical activities (those that have 0 slack) is your critical path . You can also have multiple critical paths. 

These calculations are much more manageable with ClickUp Gantt View . In your project Gantt chart , choose the Show option again, but this time, enable Critical Path and/or Slack Time . 

The critical path will show up with a different color scheme, highlighting tasks with the blocking dependency in red. 🛑

With the Slack Time option enabled, a purple striped bar will appear alongside non-critical activities to depict the wiggle room they allow for. 🟣

Another way to discern critical from non-critical tasks is by adding priority tags and color codes. For instance, you can assign critical activities with a high-priority tag and non-critical activities with a low-priority tag, and the software will color them accordingly. 

Finally, start bringing your project to life task-by-task. 🧱

As you go through tasks, you might realize some aren’t necessary or run into unexpected resource constraints. The delay caused by such events is called the critical path drag . 

Monitor activities closely to ensure adherence to the schedule and catch any plan changes in time.

In ClickUp, you can ClickUp Goals and automatically track progress. Choose between task, numerical, monetary, and True/False targets, then manage them all in one place. By closely monitoring your targets and progress, you can ensure your project stays on the right path at all times. 🛣️

Remember our house-building example from earlier? Let’s expand on it! We’ll show you how to apply the critical path analysis to a real-life example. 

We’ll be using the same ClickUp Critical Pathway Analysis Template.

Let’s start by listing all the tasks we need to take to build a house:

• Planning and design
• Site preparation
• Foundation construction
• Framing and structural work
• Installations
• Landscaping

We’ll also jot down the subtasks . For instance, in the planning and design stage, those would include:

• Hiring an architect
• Determining the house layout
• Acquiring all the permits

 We’ll also define the project’s desired start and end date —May 18 to Mar 5. 

Next, we’ll create a diagram in Whiteboard View. We’ll use the ClickUp PERT Chart Template to get a head start. Considering the dependencies and allotting larger shapes to tasks that require the longest time, we’ll create the flowchart to visualize the work ahead.

Notice how the steps fork out after the Installations step? This is to indicate that:

• Exterior painting can happen at any point after the installations
• Interior painting can’t take place until the installations have been completed
• Interior and exterior painting can be performed simultaneously, which means these tasks are parallel
• Furnishing can’t happen until the interior paint job has dried
• The landscaping stage can’t start until the exterior paint job has dried

After completing the diagram, display the dependencies in your List or Gantt View.

Next, we’ll estimate the duration of tasks , writing the number of days in the designated field in List View. Considering that information, we’ll schedule tasks and/or subtasks in Gantt View.

Finally, we’ll calculate the critical path and slack . In our case, there’s little leeway since most activities are crucial. 

As you can see in the image above, the only task with slack is the exterior painting. Once the installations are completed, exterior painting can occur at any point, provided enough time is allotted to drying and, eventually, landscaping.

Say there’s been a change of plans, and our flooring contractors asked to reschedule for the following week. In that case, we’ll move the subtask bar to its new spot. With the automatic rescheduling option activated, the other tasks will be updated accordingly! ✔️

Navigate Project Timelines Like a Pro With the Critical Path Method

The critical path method can be an excellent helping hand when dealing with a demanding project. It enables you to meticulously assess and sequence tasks, ensuring that you meet deadlines, keep the project schedule in order, maintain healthy client relationships, and drive actual progress and growth.

When your tasks are sorted out, the rest of the project falls into place.

With a tool like ClickUp , you can try CPM for free and with minimal effort. Get started today! ✨

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What Is the Critical Path Method in Project Management?

Laurenzo Overee - Guest Contributor

What is the critical path method?

Why use the critical path method, how to find the critical path of a project, critical path analysis example, optimize the critical path method for your projects, are you constantly struggling with multiple task timelines applying the critical path method can help put things into a clear perspective..

The critical path method (CPM), also known as critical path analysis, is a simple but effective project management technique. Users can apply CPM in analyzing, planning, and scheduling the most complex projects and may combine it with program evaluation and review techniques for optimal results.

CPM identifies the necessary tasks required for completing a project. The project management technique determines scheduling flexibilities to help teams handle task efficiencies while managing realistic time frames for their projects.

A collaboration between DuPont and Remington Rand UNIVAC saw the development of the CPM technique in the 1950s [ 1 ] as a solution for reducing the cost of inefficient scheduling practices.

A CPM approach usually involves the breakdown of relevant project activities, activity duration, and the relationship and dependency between tasks and logical endpoints such as project milestones.

/ Benefits of a critical path analysis

A critical path analysis enables your team to assess and analyze project activities while promoting resource management.

For instance, CPM helps teams communicate project plans and schedules, driving improved cost management and performance. Task segregation (into critical and noncritical groups) can help you prevent project bottlenecks by running certain activities concurrently.

Also, CPM presents a practical and organized base that effectively guides teams toward fulfilling project objectives with reliability. Your team may apply CPM as an accurate benchmark for future projects based on real-world expectations and observations.

/ What is a critical task?

Essentially, you may consider the critical path the longest possible sequence of activities that teams must finish on schedule to complete a project. As such, the slightest delay observed in each stage of your CPM will push back the completion of the entire project.

Ultimately, using the CPM helps teams prioritize and manage multiple contingencies and necessary fixes to keep your most complex projects running smoothly according to schedule. The CPM works well, especially during peak periods when teams juggle several projects that compete for their limited time, resource, and attention.

Essentially, your project managers and stakeholders may apply the CPM to manage expectations and realistic deadlines from the beginning of your project.

You can define the critical path of a project through a meticulous process that identifies the correlation between project activities and puts your tasks into a clearer perspective.

Although modern automated software solutions can help your team figure out the critical path of your project through algorithms, you can choose to perform a manual calculation instead for a greater understanding of your project flow.

List all project activities

A complete specified listing of your project activities provides a bird's-eye view of each task and its correlations. Applying a work breakdown structure can help systematically manage each task dependency associated with your deliverables.

Define the project dependencies

There are four primary types of dependencies in project management. These dependencies include finish-to-start, finish-to-finish, start-to-start, and start-to-finish relationships. A CPM approach requires you to identify every single dependency in every project phase to create a critical path.

Create a critical path network diagram

Modern visual workspaces can help your team create critical path network diagrams that visualize critical path networks through customizable templates for easy reference and management. These network diagrams will present a flowchart that displays how your tasks interrelate.

Estimate task duration/timeline

Your visual workspace tools can also help tabulate task durations and timelines to determine the priority of each task and how they compare with other activities in your project. You can make estimations based on historical project data, industry trends, and conjectures guided by knowledge and expertise.

Calculate the critical path

Once you have fully tabulated project task durations and timelines, you can identify the critical path as the sequence of activities with the lengthiest duration.

Determine floats

The float or slack within a project refers to the degree of flexibility for a specific task. As such, floats inform your team about the workable leeway available without impacting the overall project progress. There are two types of float to consider in your CPM: total and free.

Your CPM’s total float value equals your project’s late start time - early start time or late finish time - early finish time. For free float calculations, you may take the next task - the current task.

The total float determines the allowable time for delaying an activity from the early start date, which does not compromise the project finish date. Similarly, free float refers to the task delay time that does not affect the following tasks.

Revise as needed

Revise your CPM when required since your schedules depend on estimated activity durations. You can compare your original CPM with measured real-time CPM values of your projects for improved assessments of future projects.

A project manager begins the CPM process by considering the number of attributes for each project activity, which determines its duration.

These attributes may include:

Early Start (ES)

Late Start (LS)

Duration (the estimated time for task completion)

Early Finish (EF)

Late Finish (LF)

Float/Slack

While the manager cannot predict every possible attribute, critical path analysis can help identify them.

For instance, if a predecessor task requires 20 days for completion, it inherits the predecessor’s EF as its ES. As you work through your project with CPM, you will observe the correlations [ 2 ] between the LF and EF of activities, establishing the float value that determines the flexibility of your tasks.

CPM-based programs offer visual presentations with timeline views, customizable templates, and collaborative tools that keep multiple projects on track with consistent success. Visit Capterra’s CPM-friendly project management software to help you prioritize your project management without exception.

CPM - Critical Path Method , NetMBA

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Alex Birkett

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The Critical Path Method (CPM), also known as Critical Path Analysis (CPA), is a powerful tool in project management , providing an analytical way of organizing and scheduling the various tasks involved in a project. It is a step-by-step technique for process planning that defines critical tasks, arranges them in a sequence, and uses this structure to identify the most efficient path to project completion.

Mastering the critical path method equips a project manager with the ability to efficiently manage complex projects by identifying the longest sequence of critical tasks (the "critical path") that must be completed on time for the project to be finished by its due date. 

The critical path method identifies the longest sequence of critical tasks that must be completed on time for the project to be finished by the due date. 

A deep understanding of this method allows the manager to allocate resources effectively, manage scheduling risks, and monitor project progress, which can make the difference between success and failure in the high-stakes world of project management. 

In essence, mastery of the CPM technique is an indispensable skill that can elevate project delivery to new levels of precision and efficiency.

What is the critical path method?

The primary purpose of CPM is to determine the shortest time to complete a project. It achieves this by identifying a critical path, which is a sequence of tasks that directly impacts the project completion date. Any delay in the tasks along the critical path will lead to a delay in the entire project. Meanwhile, tasks not on the critical path may have some flexibility or "float" time, meaning they can be delayed without affecting the project’s end date.

The goal of CPM is twofold:

• To identify the tasks crucial for on-time project completion (i.e., the tasks on the critical path). This allows project managers to prioritize and monitor these tasks with extra care.
• To clarify each task's start and end dates, making it possible to allocate resources efficiently and avoid bottlenecks.

The critical path method shapes the trajectory of projects. It can gain insight into the interdependencies of tasks and influence project timelines. Project managers can navigate potential pitfalls with this approach. Additionally, CPM fosters transparent communication, enabling stakeholders and team members to align their efforts seamlessly.

Why CPM is an important strategy skill to master

Mastering the CPM is an indispensable strategy skill. At its core, CPM is not just about timelines and tasks; it's about optimizing workflow, managing risks , and ensuring that every piece of a project aligns seamlessly to achieve the overarching goals. 

Benefits of CPM include the following:

• Optimal resource allocation: CPM allows project managers to prioritize tasks based on their significance in the project timeline. It ensures critical activities receive the necessary resources, preventing delays and cost overruns.
• Enhanced risk mitigation: Project managers can preemptively identify potential bottlenecks and challenges by spotlighting the critical path. This proactive approach enables them to devise contingency plans, ensuring the project remains on track even when unforeseen issues arise.
• Informed decision-making: With a comprehensive view of the project's structure, managers are better equipped to make strategic decisions, whether it's accelerating specific tasks, reallocating resources, or negotiating deadlines with stakeholders.
• Efficient communication: The visual nature of CPM contributes to transparent communication. Stakeholders can quickly grasp the project's progress, dependencies, and potential challenges, fostering an environment of trust and collaboration.
• Cost efficiency: CPM can significantly reduce overhead costs by ensuring tasks are completed in a streamlined and timely manner. Delays often lead to financial overruns—a well-managed critical path minimizes these unexpected expenses.
• Strengthened team collaboration: Understanding task interdependencies promotes collaboration among team members. When everyone knows how their work impacts the overall project, a more cohesive and synergistic team environment is fostered.
• Consistent project delivery: Over time, the consistent application of CPM ensures projects are completed within the stipulated timeframe, establishing an organization's reputation for reliability and excellence in critical path project management.

The critical path method is about optimizing workflow, managing risks, and ensuring that every piece of a project aligns seamlessly to achieve the overarching goals. 

In essence, the CPM is more than a tool: It's a strategic skill that, when mastered, can elevate an organization's project management capabilities, driving immediate and long-term success.

Critical path method 101: how to calculate and implement CPM

This guide will walk you through the essential steps to calculate and implement CPM effectively.

1. Understand project scope and objectives

Before diving into calculations and network diagrams, it's essential first to have a thorough understanding of the project's scope and objectives. Begin by defining the project’s primary goals, deliverables, and any constraints or limitations. A foundation will guide the detailed breakdown and sequencing of tasks. For a comprehensive guide on setting up your project's foundational blueprint, explore how to create a project management plan .

2. Identify all tasks and dependencies

Once the project's scope is clear, list out all the tasks or activities required for project completion. When tasks are listed, identify the dependencies between them. Which tasks rely on the completion of others to begin or proceed? These dependencies are crucial for mapping out the project's flow.

3. Draw the network diagram

With tasks and dependencies in hand, sketch the project's network diagram. This visual representation will show all tasks, represented as nodes, and their dependencies, represented as arrows. There are multiple ways to draw such graphs, but the goal remains consistent: to visualize the flow and sequence of tasks.

Tip: Remember that the network diagram will have a starting and an ending node, representing the project's beginning and conclusion. Ensure you include all paths from beginning to end.

4. Estimate task durations

Assign a time duration for each task. These estimations can be based on historical data, expert judgment, or a combination of both. The accuracy of these durations directly affects the precision of the critical path calculation.

5. Calculate the critical path

Here's where the magic happens. The critical path is the longest path through the network diagram, indicating the shortest time to complete the project. To identify it:

• Forward pass: Calculate each task's earliest start (ES) and earliest finish (EF). Start with the initial task, which will have an ES of 0, and move forward, adding task durations to determine each subsequent EF and ES.
• Backward pass: Calculate each task's latest start (LS) and latest finish (LF). Start with the final task, which will have an LF equal to its EF, and move backward, subtracting task durations.
• Slack time: For each task, subtract its ES from its LS (or its EF from its LF) to determine its slack or float. Tasks with a slack time of zero are on the critical path.

6. Solve resource shortages

Once the critical path is identified, resource allocation becomes the focal point. You should prioritize tasks on the critical path. If resource shortages are identified, you can apply strategies like resource leveling to ensure the essential tasks of the path are not delayed.

Effective resource management ensures tasks are carried out seamlessly and without delay. For a comprehensive understanding of optimizing and managing your project resources, delve into resource management’s importance and optimization. 

7. Inform your schedule

Effective scheduling goes hand-in-hand with good time management. To ensure that every moment counts and tasks are executed efficiently, explore some time management strategies tailored for project managers.

8. Monitor and adjust

Lastly, CPM is not a set-it-and-forget-it tool. As the project progresses, monitor task completions, especially those on the critical path. If delays occur or tasks are completed ahead of schedule, adjust the project timeline and resource allocations as necessary.

It's also crucial to be aware of potential risks that could disrupt the project. To understand and be better prepared for such uncertainties, familiarize yourself with risk triggers in project management.

Tip: The world of project management is rapidly evolving with advancements in remote work and digital tools. Today, virtual project managers lead diverse global teams toward achieving common goals. In these dynamic settings, methodologies like CPM are even more vital. As we tread further into this digital age, gaining insights about the roles and benefits of a virtual project manager becomes essential for anyone in the field.

Having dissected the intricacies of the CPM, it's evident that it's not just about calculations or identifying tasks; it's about effective project visualization and communication. In an age of limited attention spans, making your project presentations interactive and engaging becomes vital. Explore interactive presentation ideas to elevate your project presentations, which can transform dense data into captivating visuals and narratives.

Skill-building: how to master the critical path method

Mastering the CPM is akin to developing a strategic mindset—it demands understanding a project's macro and micro aspects. While the fundamental principles behind CPM might be simple to grasp, truly mastering this technique involves delving deep into the nuances of critical path project management, understanding the interplay between tasks, and developing a keen sense of potential pitfalls and opportunities. 

While it's essential to get to grips with the intricacies of CPM, being effective in its application in today's business environment means embracing a data-driven mindset. A data-driven company culture is not just about gathering data but about making informed decisions based on that data. This principle aligns closely with the core tenets of CPM.

Ways to Learn CPM:

• Formal education: Consider enrolling in project management courses at universities or specialized institutions. Many offer dedicated modules or CPM courses, providing theoretical knowledge and practical exercises.
• Online courses & tutorials: GoSkills offers comprehensive courses in project management , including core topics such as CPM. GoSkills is a  PMI Authorized Training Partner and our courses include include bite-sized video lectures, quizzes, and assignments, providing an engaging learning experience.
• Project management certification: Pursue certifications like PMP (Project Management Professional) or PRINCE2. These certifications cover CPM in detail and offer a broader understanding of project management techniques and best practices.
• Hands-on practice: Theory is only half the battle. Apply CPM in real-world scenarios, starting with smaller projects. Hands-on experience is invaluable and offers insights that textbooks or courses might miss.
• Mentorship: Seek out seasoned project managers who have extensive experience with CPM. Their guidance, insights, and feedback can be instrumental in refining your understanding and application of the method.

By embracing structured learning and practical experience, you can gradually hone your expertise in the CPM, transforming it from a mere tool into a strategic skill that can profoundly impact your project management prowess.

A data-driven company culture is not just about gathering data but about making informed decisions based on that data.

For those eager to delve deeper into the world of project management and stay updated with the latest trends and insights, here are some of the best project management blogs to follow .

In the dynamic and often intricate world of project management, the critical path method (CPM) emerges as an invaluable skill, acting as both a strategic compass and a tactical roadmap. 

By highlighting the sequence of tasks that are pivotal to a project's timely completion, CPM offers project managers the clarity to navigate potential pitfalls, allocate resources wisely, and communicate effectively with stakeholders. But mastery of CPM, like any advanced skill, requires dedication, practice, and the right educational resources.

GoSkills stands as a beacon for those seeking to upskill or venture into new realms of knowledge. Whether you're refining existing expertise or stepping onto an entirely new learning path, GoSkills provides comprehensive training resources tailored to your needs. 

Ready to solidify your understanding of CPM and elevate your project management capabilities? Get certified in project management at GoSkills and set yourself apart in the ever-evolving world of business and strategy.

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Alex Birkett is the co-founder of Omniscient Digital, a premium content marketing & SEO agency. He lives in Austin, Texas with his dog Biscuit and writes at alexbirkett.com .

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Critical Path Method in Project Management (Examples & How-To)

Last updated on 30th June 2023

In this article we’re going to take a look at the Critical Path Method and answer the question: What is a critical path in project management?

Project management is the future. According to Harvard Business Review , by 2027 around 88 million people worldwide are likely to be working in project management, and the value of project-oriented economic activity will have reached $20 trillion. 

Research also shows that the majority of projects – around 65% – are unsuccessful . In other words, most projects fail and a lot of time and money is wasted. 

To avoid this failure, project managers need to manage projects effectively. And that’s where the critical path method comes in. 

So, let’s get into it…

Article Contents

What is the critical path method? A definition

The Critical Path Method (also known as CPM) is a project management technique that helps you manage your project efficiently by calculating the shortest route to entire project completion. 

The idea is that you identify all of the tasks required to complete your whole project, and then map out your tasks so that you can schedule your project in the most productive way and get an accurate project timeline. 

The Critical Path Method is ideal for complex projects that have a lot of moving parts. By breaking a big project into smaller, more manageable tasks project managers can gain a better understanding of how to get from point A – Z in the most efficient way. 

The history of the critical path method

Critical path finds its origins in the 1950s at the DuPont company . DuPont is a multinational chemical company, and has been involved in everything from developing Teflon to even playing a major role in the Manhattan Project.  

Two mathematicians (James Kelley and Morgan Walker) who were working at the DuPont company in 1957 are credited with developing the critical path algorithm. They were looking for ways to avoid the costs of plant shutdowns and restarts caused by inefficient scheduling. Their research found that if they focused their efforts on performing the right tasks at the right times, they could avoid these issues. And so, CPM was born! 

Prior to this, the company was simply flooding every problem they had with more labour in order to try and stay on schedule. By implementing the brand new critical path method instead, DuPont was able to save 25% on shutdowns .

How to implement critical path in project management

1. define the scope of the project .

The first step towards implementing the critical path method is defining the scope of your project. This means understanding all the tasks that need to be completed in order for you to consider your project a success. 

So, for step one, make a list of all your project tasks. Pretty simple! 

2. Divide your tasks 

Step two involves looking at those tasks in more detail and dividing them up so you can better understand the when, who, and how of the tasks for your project. 

This is important because some tasks will be critical tasks, some will be dependent tasks, and some tasks will be fine to work on in tandem. As a quick example, if you’re making a chicken sandwich then you can toast your bread at the same time as preparing your salad and/or sauce, but you can’t do either of those things unless the chicken is already cooked. So, the remaining tasks are dependent on the first task of cooking the chicken. 

Once you get the hang of it, the critical path method can be used for pretty much everything! 

3. Calculate the shortest route to completion  

Step three – the final step – is about finding your project’s critical path. In other words, scheduling your tasks to calculate the shortest route to completion. CPM is all about efficiency, so if you can work on tasks in parallel then you absolutely should in order to complete the project in the shortest amount of time. 

It can help to assign durations to your tasks here so that you can get a better understanding of how long everything will take. Sticking with the very simple chicken sandwich analogy, this would look something like this:

This is a very simple example of a project’s critical path, but hopefully you get the idea! 

Critical Path Method examples

Now let’s take a look at some more concrete examples of the critical path method in action.  

We’re going to give both a personal and professional example to really look at CPM from all sides and gain the best possible understanding of how to apply it when it comes to managing complex projects.

Planning a family holiday

Planning a family holiday involves a lot of different tasks, some of which can be done in tandem, while others are dependent tasks. 

The first thing you need to do is make a list of the tasks for your whole project. For example: 

• Research different locations
• Find accommodation 
• Book flights
• Book airport transfers
• Buy sunglasses
• Pack suitcase

And anything else you might want to add to the above list! 

The next step is to divide your tasks up, so Mum can be in charge of the location research and booking accommodation, Dad can be in charge of booking flights and airport transfers, and so on. 

This is also where it’s important to identify those tasks that are dependent on one another. So, for example, the airport transfers cannot be booked before the flights or accommodation. But you can shop for sunglasses and pack your suitcase at any time! 

The critical path for this project could look something like this: 

Creating an explainer video

Now for a professional example. We know all about managing explainer video projects because that’s actually how Project.co first came to be! More on that here if you’re interested . 

The tasks required for an explainer video project are: 

• Storyboarding
• Voiceover recording

Again, after listing these tasks the next step is to define and allocate them, and also find out which can be done in tandem. For example, the storyboarding process cannot start without the script. But once the script has been finalised, the voiceover can be recorded in tandem with the storyboard being created. 

If we were to calculate the critical path for an explainer video project it might look a little something like this: 

And that’s that! Why not try following these 3 steps for planning different projects in your life? It’s a great way to get used to the critical path method. 

5 Tips for successful critical path management 

1. use a project management tool .

Implementing the critical path method successfully relies on project managers having the best visibility of all tasks (critical tasks, dependent tasks, basically every single task required throughout the entire project!). Project management software can be very useful here. 

The best project management tools – like Project.co ! – allow you to not only view your tasks in a number of different ways, but allocate them to different team members, add files, notes, priority tags, and so much more. 

Project.co allows you to manage as many different projects as you want with an easy-to-use interface that you can customise to match your branding. You can also invite your clients and stakeholders to collaborate. 

2. Delegate responsibilities

Another key component of CPM is understanding who is responsible for what. This is crucially important if you have multiple tasks being completed in tandem, and it’s also necessary for dependent tasks (as team members need to know when it’s their turn to step in so that they can manage their schedule successfully). 

For project managers, this means delegating these responsibilities and overseeing the schedule to make sure everything is moving smoothly along the critical path. 

Again, project management software can help here because it makes it easy to view your entire team’s tasks at a glance. 

Project.co offers a number of ways to visualise your tasks, including kanban, list view, calendar, or the scheduler view (seen above) which allows you to view multiple team members’ tasks all on one screen.

3. Map out your project visually

Visualising your project will help you to understand how to get from point A to point Z in the quickest way possible, which is what CPM is all about. 

When using the critical path method, one of the best ways to map out your project visually is with a Gantt chart. 

A Gantt chart is essentially a bar chart that illustrates your project schedule. You can see when each task is due, which tasks are dependent on one another, and which can be completed in tandem. 

4. Create predictions

As much as we all wish for every project to sail through with no issues, the likelihood is that something unexpected will pop up. The best way to prepare for this is to make some predictions for what could go wrong and make a plan for what would happen if it did. 

We’d recommend creating a list of assumptions and risks for your project before getting started. It’s also helpful to create a list of resources that you will need so that you have a clear understanding of the scope of your project before getting started. 

5. Assign a project leader 

The critical path method is all about efficiency, which means there’s going to be a lot of moving parts at any given time. It’s important for everyone involved to be focused on their own tasks to ensure that there are no bottlenecks and the project moves forward smoothly. But, additionally, it’s also important for one person to oversee the project to ensure everything stays on track. 

In other words, to successfully implement the critical path method in project management you should assign a project leader whose sole responsibility is making sure that everyone else is managing their tasks. 

Most projects see a couple of hiccups along the way, and it’s the job of the project leader to manage these setbacks as and when they occur so that your project can still be completed as quickly and efficiently as possible.

Final thoughts

Project management techniques like the critical path method help you keep your projects on track so you can complete more projects on time and on budget. 

Interested in finding out about some more project management techniques? Take a look at this next: 10 Best Project Management Techniques for PMs in 2023 . 

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Ever find yourself making ‘guestimates’ when it comes to important task deadlines and milestones instead of making real-time updates to your overall project plan?

This is one of the most common mistakes project managers end up making with the critical path analysis method. The Project Management Body of Knowledge (PMBOK) defines this method as follows:

“The Critical Path Method is the sequence of scheduled activities that determines the duration of the project.”

Put simply, the tasks in the ‘Critical Path Method’ (CPM) cannot be initiated until the previous tasks are complete. Think of it as stringing the longest sequence of pearls (or in this case, the tasks and events) into a necklace (a.k.a critical path). Every piece is dependent on each other from start to finish to give you the desired end-result.

This project scheduling technique was developed by Morgan R. Walker and James E. Kelly in the late 1950s and is extensively used along with Gantt charts.

Did you know? This project management technique was used to execute the Manhattan Project. Let’s take a look at an interesting example to understand the critical path for making a ‘good’ versus an ‘okay’ omelet:

Here are the key points to note:

• The three steps listed below form the ‘critical’ tasks without which you will not be able to make an omelet at all. It is also essential to note that the task must be completed in the specified order to get an omelet.
• The three steps listed above form the ‘add-ons’ or non-critical tasks to the core steps, which further enhance the end result. Remember that even if you don’t end up performing these tasks, the project will get completed in time.

Let’s take a look at another example:

• In this example, Tim Tyler suggests that poaching the egg becomes the critical path or the constraining factor, whereas activities such as toasting the bread and boiling the water constitute as slack/float/free time. Basically, the latter double up as parallel paths/tasks that can be completed simultaneously using additional resources and fast-tracking the process.

Advantages of Critical Path Activities

“For me, the biggest advantage of the critical path method is that it makes risk assessment easy. If I’ve got dependencies laid out and plans change, it’s very easy to say, ‘Because you missed that deadline, the next deliverable is going to be late by X days, and that puts us beyond our plan by Y days.’ Simple. That said, I don’t think you have to fully adopt a method like the critical path to do this on projects. It’s best to adopt the parts of any method that work for your project and your team—being adaptable as a PM (project manager) will help you find true success.” – Brett Harned, digital project management consultant, writer, speaker, and community builder. When it comes to tackling complex projects, the critical path method offers a host of benefits. It is especially useful for tasks where the activity duration is easy to predict.

The main objective of the critical path method: To calculate the shortest amount of time required for sequencing the longest path of interconnected tasks that are integral to the project completion date.

The primary advantages of using this method include (but are not limited to):

• Prioritizing tasks : You can define and simplify essential and non-essential tasks on the path in a visual manner, which is easy to comprehend.
• Preventing delays : You can prioritize tasks effectively and allot the time required to complete the project, keeping in mind the longest sequence possible.
• Enhancing productivity : The CPM (critical path method) helps to allocate resources optimally.
• Optimizing efficiency : It allows you to reschedule low-priority tasks, thereby freeing up the team’s bandwidth.
• Tracking and managing tasks efficiently : You can make modifications to the project schedule and track the progress in real-time.

“The critical path method brings an important level of clarity to your project. It is a visual depiction of the fragility of the balance of your constraints: If one of the activities on the path gets delayed, your project gets delayed. It is also a great way to determine where to invest resources if the project has fallen behind schedule.” – Cesar Abeid, host of the Project Management for the Masses Podcast

Disadvantages of the Critical Path Method

• Like with most planned schedules, delays and bottlenecks are commonplace. And as such, this method does not factor in the same.
• Additionally, it also does not take into account in-depth details with respect to people, resources, and budget.
• Estimating task durations with exacting precision can be difficult.

Creating a Critical Path: The Basics

Step 1 : You specify the activities and project deliverables using the work breakdown structure (WBS) and detail the longest sequence possible.

Expert tip : Try making the WBS as detailed as possible as it serves as the foundation of your critical path.

Step 2 : List the dependent and concurrent tasks and identify which tasks depend on each other to create an activity sequence.

Handy tip : To stay ahead of task priority, project managers should track each task progression as the team goes about performing it.

Step 3 : Next, you need to create a critical path analysis chart based on the tasks identified along with the dependencies. To get started, first make a list of the activity sequences and create different boxes for each task. You also need to put in arrows to signify the task dependency.

Step 4 : Figure out the longest time duration for each activity. You can use data from experience and knowledge, past projects, or industry benchmarks to arrive at a satisfactory number. Alternatively, you can take the average of the following three cases to arrive at an accurate project time estimate:

• Ideal-case scenario or the shortest duration (A)
• Normal scenario or the expected duration (B)
• Worst-case scenario or the longest duration (C)
• Activity Duration = A + B + C / 3

That’s not all. You can also use the Forward Pass/Backward Pass technique, earliest start and finish times, and the latest start and finish times for each activity to understand the longest duration:

• Early Start (ES): Earliest date the activity can start
• Early Finish (EF): The earliest date that the activity can finish: ES + Duration of the activity.
• Late Finish (LF): Latest date/time that the activity can finish without causing a delay to the project.
• Late Start (LS): The latest date that the activity can start without causing a delay to the project completion date: LF – Duration of the activity.

Step 5 : Finally, you calculate the critical path. Here’s an example of the critical path for a construction project:

Handy tip : Putting the critical path project management on auto-pilot is futile. It is imperative to ensure no other task gets delayed to the extent that it becomes a critical path task. Additionally, you need to keep updating the critical path diagram to showcase real-time progress.

In a Nutshell: CPM the Cornerstone of Project Management Today

“The critical path is just a fancy way of saying, ‘How long does each task take before you can finish the project? Use this information to figure out the project’s end date.’ If a task takes longer than anticipated, the end date is pushed back. There are some tasks that don’t immediately impact the project’s end date that can be pushed back for some time. There are a whole bunch of calculations that go into figuring out the what-ifs, forecasting, and scheduling, but that’s where project management software comes in and makes everyone’s lives easier. ” – Rachel Burger, Capterra Construction

The CPM method is essentially an algorithm for decision-making. By employing key factors such as the task’s start time, duration, and end-time, you can chart the ‘critical tasks’ needed for successful and on-time project completion. Most project management software solutions today can easily help you create a critical path for important projects in day-to-day life.

That said, at its heart, this method serves as a godsend for time-critical projects and for projects that are smaller in scope and size. So if you’re looking to complete projects on-time with greater efficiency, this should be your go-to project management methodology.

Related Article:

A beginner’s guide to the critical path method in project management

Last updated

21 December 2023

Reviewed by

Mary Mikhail

Large and complex projects require the use of many materials and working parts. Without a clear plan for undertaking such a job, it’s easy to become overwhelmed and skip important tasks. When this happens, your project is less likely to meet critical deadlines. Or it could fail completely.

CPM is used to identify the vital aspects of any project and its dependent factors to define tasks and ensure the project is completed accurately and on time.

Read on to find out exactly what CPM is and how to use it. You’ll also find some examples of successful use cases.

• What is the critical path method?

The critical path method is a project management method used for calculating, planning, and scheduling large or complex projects. It enables project planners and teams to create a clear roadmap of the jobs or activities that are critical to completing a project on time. By identifying and scheduling fundamental tasks, project managers can assign a specific job’s start time, expected duration, and finish time.

Every project contains vital tasks that determine whether it’s completed on time. If any of these tasks fall behind schedule, so does the whole project.

CPM is a step-by-step plan for identifying critical tasks and creating a clear timeline (or path) in which these tasks will be completed. The schedule of these core project steps is the critical path. Once these tasks are scheduled, you can add other (less crucial) activities to the timeline.

What is a critical task?

A critical task is a job or activity central to a project’s timeline. Other activities will also be delayed if these central tasks are not completed on time.

Every project includes core tasks that must be finished before dependent tasks can begin. For example, you can’t put a roof on a home if the frame hasn’t been erected. In essence, critical tasks are the activities that must be carried out as planned to avoid disrupting the project timeline.

Why must non-critical tasks be monitored?

Critical tasks aren’t the only tasks you’ll need to take care of to complete an entire project. You’ll need to carry out other jobs, too. However, these can be executed less urgently. Since they aren’t core steps, you can choose to delay them until they fit into the schedule better.

By monitoring non-critical tasks alongside the undertaking of critical tasks, you can make informed decisions about when each task should be completed. This approach enables teams to complete several tasks simultaneously without critical delays.

Where was CPM first used?

While the US Navy’s Fleet Ballistic Missile (Polaris) Program was running behind schedule, the chemical company DuPont faced delays in plant turnarounds. Those running these projects needed a technique to get them back on track and deliver them as planned.

The developers of the Polaris Program created a solution called the project evaluation and review technique (PERT). DuPont developed the critical path method.

The PERT method calculates three different time estimations to determine the most accurate duration of each task. DuPont’s CPM plan uses a single time duration for the entire task to measure extra costs that would accumulate if the project duration is decreased.

Why is CPM important in project management?

CPM creates a project roadmap that establishes the longest sequence of tasks that must be executed to complete an entire project. By defining core tasks and the tasks that depend on them, project managers can outline the timeframe in which the project can be successfully executed. This helps reduce noise and align priorities, enabling multiple teams to complete tasks simultaneously without delays.

When should you use critical path analysis?

Critical path analysis is a way to refer to the early stages of CPM. CPM typically aims to develop an accurate project schedule, so the process occurs before the project’s start date—perhaps during the project’s planning phase or even during the process of developing a bid or project proposal.

Understanding a project’s critical path can help project managers estimate costs and resources and develop a predictable schedule.

• How to calculate the critical path

Virtually every project is planned based on completing the job as quickly and cost-effectively as possible without compromising quality. This approach offers the best return on investment (ROI) and ensures minimal resource waste. You can use CPM to make informed decisions about the best way to achieve this goal.

To calculate the critical path, start by identifying all tasks in the project. Once you have a clear idea of everything that needs to be done, you can assign levels of urgency based on dependencies and the estimated time needed for each task.

Take these steps to calculate your project’s critical path:

Define all the tasks required to complete the project.

Define the time requirements for each step based on existing knowledge or industry standards.

Establish dependencies (tasks that must be completed before another specific step can begin) for each task.

Identify which activities must be completed on time to avoid delays due to dependencies. These are your critical tasks.

Align critical paths in a sequential timeline with assigned start and finish times.

The significance of float or slack in CPM

Projects are rarely executed exactly as planned. Delays, resource constraints, unexpected incidents, and scope creep create conditions that cause any task to take longer than planned. To prepare for such issues, project managers should consider the consequences of delays.

The time a task can be delayed for without affecting dependent tasks or delaying the overall project is referred to as float or slack .

Activities on the critical path have zero float. If a critical task is delayed, it will immediately affect dependent tasks and the completion of the project. However, many other tasks can have varying levels of float.

High-float tasks can be delayed with minimal consequences. They simply need to be completed before the project deadline or before they affect another non-critical task. Label high-float tasks as low priority so that you focus on assigning resources to critical tasks. When team members become available, they can take care of high-float tasks while other tasks progress simultaneously.

Identifying slack for each task lets you assign start times and juggle tasks without affecting the project’s timespan.

• Planning for unexpected contingencies and constraints

Large and complex projects can take weeks, months, or even years to complete. Long time frames combined with project intricacies may create unexpected changes that force you to expedite some tasks and postpone others.

To take these contingencies in your stride, you’ll need methods in place to address how such issues impact the overall project timeline.

The two most common methods of dealing with contingencies and constraints when using CPM are fast-tracking and crashing.

Fast-tracking

Fast-tracking is easy to understand if you’re used to multi-tasking to stay on schedule. When deadlines are looming, fast-tracking is the process of executing multiple jobs on the critical path simultaneously. This approach requires you to dilute resources to complete multiple jobs at once and can only be used for activities without dependencies.

When you need to meet updated or emergency deadlines, crashing is the process of allocating more resources to speed up activities. You might bring in more professionals or use resources from tasks with high floats.

Crashing is typically used in emergencies because it can impact critical tasks and project scope . When the project scope is affected, you’ll need to inform all project stakeholders .

• Comparing CPM to other methods

CPM isn’t the only project management method for scheduling and prioritizing project tasks. Comparable methods are used to evaluate the duration and dependencies of specific tasks. While these methods have similarities, their overarching goals differ.

Critical path method vs Gantt charts

Gantt charts map out projected activities and track them against a set timeline. Like CPM, they show dependencies between tasks, and you can use them to create a timeline. However, there are distinct differences between the goals of CPM and Gantt charts and how they are displayed.

CPM is displayed as a network diagram, while Gantt charts are displayed as a horizontal bar chart.

Gantt charts show the resources required for each activity.

Gantt charts plot activities on a timescale, while CPM plots them on a network diagram with an estimated time duration for each task.

CPM identifies critical and non-critical paths and calculates project duration. Gantt charts are designed to visualize how project activities are progressing.

Critical path method vs PERT

The project evaluation and review technique was developed around the same time as CPM to solve similar issues, but the techniques are quite different.

CPM and PERT are both used to evaluate project duration. They identify dependencies and provide an estimated duration for each task. However, they have several notable differences in execution.

PERT is used to estimate the time required to complete activities, while CPM is used when task durations are already estimated.

CPM is designed to evaluate time–cost trade-offs and establish priorities, while PERT focuses on meeting deadlines or shortening a project’s duration.

PERT has three estimates for each activity, while CPM only has one.

PERT is often used for projects that have significant uncertainty, while CPM is better suited to projects where tasks are well-defined.

• CPM benefits

The critical path method is an excellent project management tool to help you deliver your project on time and within budget. It can be useful in recognizing potential delays and scope creep while creating a clearly defined schedule for the project.

Below are some of the most common advantages of using CPM for large and complex projects:

Helps prioritize tasks

CPM’s overarching goal is to identify essential tasks and ensure their timely completion.

Identifying the critical path enables you to clarify which tasks depend on one another, establishing the order in which they must be completed.

Once the critical path is defined, you can prioritize the non-critical tasks based on their slack level. The approach eliminates the “noise” in a multi-faceted project and keeps teams on track.

Improves team communication

Large projects typically require the participation of multiple teams with different specialties. These teams work together to establish an accurate critical path. When the resulting CPM diagram is used as a single source of truth, every participant in the project will have similar expectations of how the work schedule will play out.

Optimizes efficiency

CPM is used to identify the earliest possible starting point and the latest acceptable finishing point for each project task.

Mapping out a schedule with accurate timeframes and dependencies can enable project managers to identify areas that could shorten the critical path. You might achieve this by assigning more people to the job or juggling non-critical tasks for optimal efficiency.

Helps create accurate schedules when paired with PERT

PERT and CPM have distinct differences that naturally complement each other. While both techniques are designed to evaluate time, PERT is focused on time management, while CPM addresses how the project timeline affects the budget.

PERT charts contain three estimates for each task, making it easier to discover potential risks and avoid delays.

Helps map out project plans when paired with Gantt

Gantt charts plot project tasks on a time schedule in a horizontal graph, which acts as a visual communication tool. They can be used to track actual progress against planned progress to help maintain an accurate schedule.

When combined with CPM, Gantt charts give you a more detailed view of the product path, including the required resources for each task.

• How to use the critical path method

Now that you have a clear understanding of the CPM’s purpose, you can apply the process to devise an accurate project schedule. Follow the steps below to plan your project using the critical path method:

1. List project activities

Begin by evaluating your complete project and breaking down the necessary work into manageable steps. Create an ordered list of all the tasks required to complete the job.

2. Identify task dependencies

Some tasks can’t begin until others are finished. Examine your list of tasks and define each activity’s immediate predecessor. Some tasks won’t have dependencies, but critical tasks often do.

3. Create a critical path diagram

Identifying dependencies enables you to create a sequence of events. Create a chart that maps out the tasks in the order they should be completed. The network diagram should include arrows or symbols to identify dependencies.

4. Estimate the timeline for each activity

Estimate the time required to complete each task on the diagram using prior experience or industry knowledge.

Use the PERT method to accurately calculate the best-case estimate, the most likely estimate, and the worst-case estimate. These three values can be used to determine slack more accurately and develop a precise timeline.

5. Use the critical path formula

Once you’ve established estimated durations for each task, you can develop a timeline for the entire project using the critical path algorithm. The critical path formula uses a forward pass and a backward pass to establish a timeline.

The forward pass uses a specified start date as the earliest start (ES) for the first task and calculates the earliest finish (EF) by adding the estimated duration. The process proceeds through the schedule by defining the ES as the highest EF of immediate predecessors.

The backward pass calculates late start (LS) and late finish (LF) dates using the lowest LS value from immediate successors to calculate LF. This pass starts with the last scheduled activity and moves backward through the schedule.

Here’s a simple example using a forward pass and backward pass to establish a timeline for a project with three activities: A, B, and C. The numbers represent the duration of each activity in days. Each activity is dependent on the one before it—B is dependent on A, and C is dependent on B.

Here are the activity durations:

Activity A: 3 days

Activity B: 2 days

Activity C: 4 days

Forward pass

Start at the beginning. Set the ES for the first activity to 0.

Activity A:

Duration = 3

EF = ES + Duration = 3

Activity B:

ES = EF of A = 3

Duration = 2

EF = ES + Duration = 5

Activity C:

ES = EF of B = 5

Duration = 4

EF = ES + Duration = 9

The EF of C is the project duration in this case.

Backward pass

Start at the end. The project duration is the LF of the last activity.

LF = EF of C = 9

LS = LF - Duration = 5

LF = LS of C = 5

LS = LF - Duration = 3

LF = LS of B = 3

LS = LF - Duration = 0

You now have the ES, EF, LS, and LF for each activity.

Critical path

The critical path is the path with zero slack (total float). Activities on the critical path have the same ES as LS and the same EF as LF.

In this example, the critical path is A -> B -> C. The project duration is nine days, and any delay in activities on this path will directly affect the project completion date. Activities A and C are “critical” in the sense that they must be completed on time to avoid delaying the project.

6. Identify the critical path

Define critical tasks as those with no slack level (zero float) and align these tasks into a schedule based on immediate dependencies. Assign a time duration to each critical task derived from the formula used in the previous step. The activity sequence with the longest duration is the critical path.

7. Revise during execution

While the critical path is determined during the planning phase, it shouldn’t be set in stone. Update the critical path chart or diagram as you execute the project. As changes occur in the project schedule, you can define ways to address delays. You can develop a more accurate schedule by updating it to account for constraints and contingencies.

• Examples of the critical path method

The critical path method can be used to manage nearly any type of project in which you can estimate the duration time of specific tasks. Observing examples of CPM in practice can help you clearly visualize how the technique is used.

CPM in construction

Building a house is one of the most common examples used to clearly illustrate project planning with dependencies and potential time constraints. Construction is a complex project with many dependencies.

Conduct excavation

Build a foundation

Construct a wooden frame

Lay brickwork

Box in the walls

Build the roof

Wire electricity

Install plumbing

Install heating and ventilation

Lay flooring

Finish wall carpentry

Fasten gutters and downspouts

Install plumbing fixtures

Finish interior carpentry

Put gutters and downspouts in place

Identifying dependencies

Construction involves many dependencies.

The core jobs will outline your project’s critical path. The process of pouring footers and building a foundation is dependent on the starting task—excavation. Similarly, framing is a critical task that must be completed before walls can be constructed and the roof can be built. However, the brickwork and the electricity can be reasonably postponed until a convenient time.

Jobs with float can be executed in parallel to dependent tasks. For example, an available worker can lay brickwork while others are building the roof.

Therefore, jobs on the critical path are most likely to be excavation, foundation, framing, roof, rough wiring, and rough plumbing. The other tasks in the project will have some float and can run parallel to other tasks.

CPM for shorter tasks

It sometimes helps to consider how project management works from a simpler perspective. If you’re a practiced cook, you’re accustomed to the process of taking care of multiple tasks while being mindful of dependencies. Yet, an inexperienced cook could forget essential steps.

Imagine preparing breakfast for friends. You plan to cook pancakes, eggs, and bacon. You’ll prepare many of these foods in tandem, but some steps have dependencies.

Purchase eggs, bacon, flour, milk, maple syrup, oil, and butter

Preheat the oven to 200 degrees to keep the food warm until serving time

Measure and mix the flour, eggs, oil, and milk to create pancake batter

Fry the bacon

Cook the pancakes

Season the eggs

Fry the eggs

Keep the pancakes warm in the oven while you cook the other foods

Top the pancakes with maple syrup

Again, your starting step for this project is a critical task that must be completed before any other activities can begin: purchasing the ingredients.

Moving forward, you can’t cook the pancakes before mixing the batter. However, since you plan to keep food warm in your preheated oven, you can fry the bacon while you’re mixing the batter or flipping the pancakes. Ideally, you would prepare the eggs last so they will be at the optimal temperature when the meal is served.

The jobs on the critical path are most likely to include buying ingredients, preheating the oven, mixing the batter, and frying the eggs. Other tasks can be completed in parallel to these essential steps.

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Understanding critical paths in project management

A critical path is a method used by project managers to prioritize tasks and deliver a project on time. But unlike most project management concepts, the title of this one doesn’t give much away.

That’s why we’ve created this no-nonsense guide to help you understand what critical paths are, why they’re important, and how to implement them. Plus, we’ll show you how the critical path feature in monday work management can make your job easier.

What is a critical path?

A critical path is the longest sequence of dependent tasks that must be completed to execute a project. The tasks are called critical activities because the whole project runs over if they’re delayed.

For example, if you’re building a house, the critical path might include activities like digging the foundations, building the walls, and installing the roof. If any of these critical activities fall behind schedule the whole project gets delayed.

Project managers use the critical path method (CPM) to find the critical path. The CPM — also known as critical path analysis (CPA) — is a project management technique used to plan and schedule complex projects. It’s an algorithm that identifies the longest sequence of dependent activities and measures the time required to complete them from start to finish.

What does a critical path look like?

Asking what a critical path looks like is like asking, “how long is a piece of string?” — i.e. there’s no definitive answer.

Traditionally, the critical path was a flow chart. For example, some house-building activities take longer than others, so the critical path highlights the longest duration:

[Image source]

A more complex diagram might look like this:

Nowadays, other more visually appealing ways of presenting a critical path exist. For example, using a Gantt chart allows you to visualize the critical activities:

Critical path vs. critical chain

Critical path and critical chain are two different approaches to completing a project.

The critical chain methodology pinpoints the bottlenecks or limiting factors that can cause businesses to miss project deadlines. It focuses on monitoring the use of resources — like materials and labor. For example, a project manager might delay the start of one task so that a skilled worker does not have to perform two tasks at the same time.

The critical path focuses on task management, assumes unlimited resources, and identifies the longest track of tasks. It helps identify tasks that may cause project delays and guides project managers to take preventive measures from the start.

On the other hand, the critical chain focuses on resource and buffer management, assumes limited resources, and identifies the longest chain of dependent events. It inserts buffers between dependent events to protect the project from delays.

Critical path vs. critical activity

Critical path and critical activity are related concepts in project management , both determined by the critical path method (CPM).

The critical path is the longest sequence of tasks that must be completed for the project and comprises critical activities. Any delay in completing tasks on the critical path will also delay the project.

A critical activity is a specific scheduled activity that is part of the critical path. It’s essential to the project’s timeline, and any delay in completing a critical activity will delay the entire project.

For example, if it takes twice as long to dig the foundations for a new house, then the entire house building project gets delayed. A critical activity typically has zero float, meaning there’s no flexibility in the start or finish dates.

Critical path vs. PERT

The critical path and PERT (Program Evaluation and Review Technique) are tools for planning and controlling projects.

PERT is a framework to map out task dependencies and estimate how long a project will last. It’s a statistical tool to visualize the overall project schedule — not just the critical path — and shows the relationship between tasks as well as the overall project duration.

For example, a project with seven key activities and a total project duration of 14 days, could have a chart that looks like this:

The critical path is used to schedule and manage project tasks, focusing on the longest sequence of tasks and considering task dependencies and slack time. It is suitable for projects with predictable task durations.

On the other hand, PERT is used to calculate the time required to complete project activities, especially when task durations are variable and uncertain. It allows for flexibility in project scheduling and focuses on time estimation and uncertainty.

Critical path vs. Gantt chart

The critical path and Gantt chart are both project management visualization tools, but they serve different purposes.

The critical path helps schedule and manage project tasks, taking into account task dependencies and slack time. It’s suitable for projects with predictable task durations.

On the other hand, a Gantt chart provides a visual overview of tasks, durations, and dependencies in a project schedule. It helps track progress, allocate resources, and communicate project timelines.

While a Gantt chart can highlight the critical path, its primary purpose is to visualize the project schedule.

What are the benefits of the critical path method?

The critical path method (CPM) offers improved project planning, enhanced scheduling, clearer communication, effective resource management, tighter cost control, risk detection, and better project management.

1. Enhances project planning

The CPM provides a structured approach to project planning by identifying the sequence of activities and their dependencies. This helps project managers create a realistic and robust project schedule .

2. Helps prioritize tasks

The CPM identifies the critical tasks and determines the critical path. This helps project managers prioritize tasks effectively and determine where and how to allocate resources.

3. Improves team communication

The CPM requires input from key stakeholders, including team members and subcontractors. This collaboration ensures everyone understands the project timeline and dependencies, leading to better communication and coordination.

4. Facilitates more effective resource management

The CPM helps project managers identify resource requirements for each activity. Project managers can allocate resources efficiently by understanding the critical path and resource dependencies, minimizing bottlenecks and unexpected delays.

5. Tightens cost control

The CPM assists project managers in controlling costs by allocating the right resources to the right places. This reduces the chances of unexpected delays that may incur additional costs.

6. Detects potential risks

The CPM allows project managers to identify potential risks and their impact on the project schedule. By analyzing the critical path and considering the float or slack time, project managers can predict the effects of delays and make adjustments to mitigate risks.

7. Improves project management

The CPM enables project managers to clearly communicate project plans, schedules, and performance. This clarity helps them monitor progress, identify issues, and make informed decisions.

To summarize: by utilizing the CPM, project managers can optimize project timelines, allocate resources effectively, and mitigate risks, leading to successful projects.

How to find the critical path

Now, let’s identify the critical path from start to finish.

1. List all your project tasks

Before you even think about a critical path, you need to list what tasks to include in the project — i.e. your work breakdown structure .

Spend some time speaking with stakeholders to confirm the project details. Once you have all the information, you can identify all the activities that must happen to complete the project.

2. Put all the tasks in order

Once you’ve identified the tasks, it’s time to put them in chronological order and identify any task dependencies . This will help you work out the project timeline.

So what’s the best way to put them in order?

Whether you’d prefer to create a project roadmap, tracker, or overview, using an efficient, easy-to-use work management software — like monday work management — simplifies the process by giving you a clear visualization of all your tasks:

3. Estimate how long each task will take

There are several ways to estimate activity duration. To save you from sifting through all the methods out there, we’ve outlined our top three:

• Bottom-up estimating : Add up the estimates of the lowest-level work tasks to arrive at your summary total. Bottom-up estimates take more time to complete, but they also are more accurate than other estimates.
• Comparative estimating : Base your estimates on similar work or projects completed in the past. If you used time tracking in previous tasks, you’ll see precisely how long they took.
• Parametric estimating : Calculate a portion of the work and then multiply to get the overall estimate — e.g. if you believe one ad takes 2 hours and you have five ads to do, it should take 10 hours in total.

Read also: Bottom-up vs. top-down

4. Find all the potential ‘paths’ or ‘strings’

Any project can have multiple paths or strings of connected and dependent tasks.

This part of the process involves finding all these possible paths and calculating how long each one will take so that you can pinpoint the one with the longest duration.

By hand, this can be a headache with a high chance of error, which is not ideal. Fortunately, project management platforms, like monday work management, can do this automatically.

5. Identify the critical path

Now for the main event — it’s time to find the critical path.

Once you — or your work management software — have listed all the paths and strings, you need to identify the longest path through the project from start to finish.

So, if you’ve got a string of tasks that takes eight days, one that takes six days, and another that takes 12, then the 12-day string is the critical path. It’s the one that can’t have any delays without moving out your project end date.

6. Monitor the critical path

The critical path can, and most likely will, change throughout the project. Some tasks may take longer than expected, or new tasks get added over time.

Any changes to the project can have a knock-on effect on the critical path. This means you’ll need to check continuously throughout the project and update your critical path diagram accordingly.

We know it’s not ideal. One of the limitations of using the critical path project management method is its lack of flexibility. That’s why we created a critical path feature in monday work management that accounts for more flexibility.

Manage your critical paths with monday work management

The monday work management critical path feature makes your team more aware and efficient by visually displaying each project’s duration.

Once you add this feature to your Gantt Chart, it highlights the critical path in your project’s timeline — the events that must be completed on time for the overall project to finish on schedule.

Moreover, the software monitors any changes in critical path activity and automatically updates the current critical path in your project plan , so you don’t have to.

Start identifying critical paths today

So there you have it — a simple, no-nonsense guide to critical paths, including their definition, benefits, and how to identify them in your projects.

Now you know what’s what, why not check out some project management software that enables you to implement critical paths within your projects?

Critical path FAQs

Why is the critical path important in project management.

The critical path is important in project management because it helps estimate the project duration accurately, identify critical activities that must be completed on time, and highlight task dependencies, resource constraints, and potential risks. 

What are non-critical activities?

Non-critical activities are tasks that can be delayed beyond their allotted deadline without affecting the project's overall duration. These activities have slack time and are not part of the critical path.

Can a project have multiple critical paths?

Yes, a project can have multiple critical paths. In complex projects, you can have multiple sequences of activities that are equally critical and must be completed on time for the project to run on schedule.

• Project schedule management

Critical Path Method (CPM) in Project Management: Explained

The critical path method (CPM) is a project scheduling algorithm used to calculate the total time needed to complete a project.

This makes it a great tool for any project manager to add to their arsenal. Best of all, once you learn the terminology and can look past the intimidating diagrams, you’ll find that CPM is surprisingly simple to use.

In this guide, we’ll teach you everything you need to know to use the critical path method, including:

• What the critical path is,
• How to calculate the critical path,
• What the benefits of CPM are, and
• How CPM is different from PERT and Gantt charts.

If you’re wholly new to CPM and don’t understand the associated technical terminology — like early start (ES) or total float (TF) — please refer to the CPM terminology section located at the end of this guide.

Table of Contents

What is the critical path method (CPM)?

The critical path method is a scheduling algorithm that calculates how long a project will take to complete by identifying its critical path. 

The critical path is the longest sequence of dependent activities within a project . CPM also highlights how much extra time you have to perform activities that aren’t on the critical path, thereby showing you where you can be flexible without missing the deadline. 

This allows you to prioritize tasks and manage resources in a way that supports progress toward project completion.

How to find the critical path + example

Critical path method calculations are exceedingly simple — it’s just addition and subtraction, most commonly using days as the unit of measurement. 

Using the critical path method technique requires you to follow these 4 steps:

• Create a Work Breakdown Structure,
• Create a CPM diagram using task dependencies ,
• Do a forward pass to identify the critical path, and
• Do a backward pass to calculate float.

So, let’s go through the critical path method step-by-step, using a YouTube video production project as an example.

Step #1: Create a Work Breakdown Structure

Step 1 of using the critical path method is creating a Work Breakdown Structure for your project.

Work Breakdown Structures are a complex subject in their own right, so we suggest reading our Work Breakdown Structure guide if you want to know more.

The short of it is this — a WBS is a hierarchical list of all tasks you’ll need to do to finish the project . 

Work Breakdown Structures are usually presented in the form of a tree diagram, but for the sake of CPM, you can just make a list.

You should also note down the duration of each task. Unfortunately, CPM doesn’t help you get this data, so it’s up to you how to decide on the duration for each task — estimates, guesstimates, previous experiences, etc.

To make our YouTube video, we’ll need a simple WBS like this:

Step #2: Create a CPM diagram

Step 2 of using the critical path method is drawing up a task diagram.

Once you’ve got the project task list and task durations ready, create an activity node for each activity.

To see how an activity node should look and what data goes where, refer to the terminology section at the end of this guide.

At this early stage, nodes will only contain their activity name and/or designation and duration:

• (c) Write a script, 3 days
• (g) Record the footage, 10 days

Connect the activity nodes with arrows to signify task dependencies. 

For example, editing a script is dependent on writing a script. The nodes will naturally branch out, but they will all converge to mark project completion.

With that done, you’ll be ready to start calculating the forward pass. 

The image below shows what the CPM diagram of our project should look like at this point. We’ll fill in the blanks as we go through steps 3 and 4. 

Step #3: Do a forward pass

Step 3 of using the critical path method is doing a forward pass.

The forward pass is the act of calculating the early start (ES) and early finish (EF) times of all activities and highlighting the critical path. 

To calculate EF for each task, we will use the following formula: 

EF = ES + Dur

What keeps this formula simple is the fact that the starting activity always has an ES time of 0.

So, given that task (a) Research the topic has an ES of 0 and a duration of 5 days, its EF is 5.

EF = ES + Dur = 5 + 0 = 5

The EF of one activity is automatically assigned as the ES of all tasks immediately dependent on it. 

What this means is that the ES of task (b) Create a concept is 5 — the earliest you can start doing this task is on day 5. Since task (b) has a duration of 3 days, its EF is 8.

EF = ES + Dur = 5 + 3 = 8

Now, once you’ve finished work on task (b), you can immediately start working on two independent tasks — (c) Write a script and (g) Record the footage . Both of these tasks will have the same ES of 8, but different EF times.

EF = ES + Dur = 8 + 4 = 12

EF = ES + Dur = 8 + 10 = 18

Once you’ve done this for all activities, you can see which sequence of activities takes the longest to complete. 

Keep in mind that we are calculating the total time needed for project completion, not the number of activities.

In this example, the sequence of nodes that will take the longest to complete is (a)-(g)-(h)-(i)-(k) — this is the critical path . 

The sum total duration of this chain of activities is 25 days:

5 + 3 + 10 + 5 + 1 + 1 = 25

No matter what you do, you will not be able to complete the project in under 25 days, since that’s how much time all the tasks on the critical path require.

Step #4: Do a backward pass

Step 4 of using the critical path method is doing a backward pass.

Once we’ve finished calculating the forward pass to identify the critical path, it’s time to do a backward pass that’s used to calculate float.

Activities on the critical path don’t have float. 

If they get delayed or prolonged by even a day, the entire project gets delayed by the same amount. 

But, activities that aren’t on the critical path have some wiggle room.

To calculate how much float other activities have, you’ll first need to calculate their late finish (LF) and late start (LS) times. 

The LF of a node is equal to the LS of the subsequent one. 

Activities on the critical path have equal values for their ES and LS, so we’ll take the final node as our starting point.

Therefore, node (j) Promote the video on social media has an LF of 24, as this is the LS value of node (k) Upload the video to YouTube . To calculate its LS, we use the following equation:

LS = LF – Dur = 24 – 3 = 21

We can then use the LS of task (j) to calculate the LF of (e) Create a title , and so on until we’ve done this for all tasks.

Now all that’s left to do is to calculate the float.

To do this, take any task and run it through either of these formulas:

TF = LF – EF 

TF = LS – ES 

Whichever formula you choose, you’ll get the same result. Let’s demonstrate this on task (j) Promote the video on social media :

TF = LF – EF = 24 – 16 = 8

TF = LS – ES = 21 – 13 = 8

What this shows us is that, even if promoting the video takes longer than expected, you won’t have any trouble since you have 8 days of breathing room to complete that task.

💡 Plaky Pro Tip

CPM is one of the most used techniques in project management. Check out some other popular project management tools here:

• 10 Essential Project Management Techniques to Use in 2024

The CPM example — key takeaways

So, let’s walk through this example of the critical path method once more, this time without the math explainers.

We figured out which tasks need to be done to create a video from scratch and upload it to YouTube.

Then, we assigned a duration to each task and linked them for dependencies.

This is all the data we needed to do all the calculations necessary for using the critical path method.

The calculations showed us that the project would take at least 25 days to complete, and that’s if no tasks on the critical path get delayed.

It also showed us that work on the script and voiceover recording does not constitute a bottleneck in this project. The same goes for creating a title and promoting the video. 

Knowing that these tasks have float could help us distribute our efforts optimally. It would also enable us to divert some resources from tasks that have float to those that don’t and are struggling. 

For example, if the person capturing the footage needed help recording some segments, they could ask the scriptwriter for help without compromising the overall project progress. 

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Why is the critical path method used?

The advantages of the critical path method are many, but we can divide them into 2 broad categories:

• Primary, and

The primary advantages of the critical path method 

The first reason why you’d use the critical path method in project management is to calculate how long it will take to complete and create a schedule.

The other main advantage of the byproduct of creating the schedule and calculating the critical path leads to the other main advantages of the CPM project management technique — float. Namely, CPM shows you which project tasks can be extended without pushing back the project deadline .

Understanding float and using it to your advantage is where the real magic kicks in.

If and when a project encounters setbacks, the project manager can use float to formulate countermeasures that will bring the project back on track. 

For example, if a task that’s on the critical path is running late, they can divert resources from non-critical path tasks to speed it up. Even if this isn’t the ideal countermeasure, something has to be done because critical path tasks are the biggest progress bottlenecks in a project. 

On the other hand, if a task that’s not on the critical path is running late, they may not need to react in any way, provided the task has sufficient float. At the very least, they’ll know not to take resources away from tasks that are on the critical path — which would result in an even worse problem.

To learn all about the different types of float in project management and see examples of each type, read this guide:

• What is float in project management?  

The secondary advantages of the critical path method

Another thing that CPM has going for it is that it’s easy to use. You just need to know what tasks need to be done, how they relate to one another, and how long each task will take. After that, it’s just a matter of simple addition and subtraction. 

Compared to input data used by other scheduling algorithms — like PERT, for example — this is as simple as it gets.

Lastly, CPM has a good track record. It was developed back in the 1950s by E.I. duPont de Nemours, a chemical company that had been suffering from production delays, and has been used ever since. 

The fact of the matter is that you don’t get to survive as a scheduling technique for over 70 years if you don’t give good results.

And, while the specifics of how to portray the CPM diagram have changed since then, the core of CPM has remained the same. 

In other words, it is still one of the best ways to map out a project schedule and increase its efficiency.

The disadvantages of CPM

Now, for all its benefits, CPM does carry some drawbacks that are worth pointing out.

First of all, CPM uses task duration as its primary input, but it doesn’t tell you how to estimate these durations. Meanwhile, any errors in these estimates can affect the calculations. This means that if your task duration assumptions are off, your calculations will be off as well.

Secondly, CPM assumes that time is the only constrained resource. Let’s refer back to the video production project example. If one person needs to do everything on their own, the critical path diagram is useless since one person can’t do 3 tasks at the same time.

If you need a scheduling algorithm that can account for multiple resource constraints, we suggest reading our guide on Critical Chain Project Management.

• What is Critical Chain Project Management (CCPM)

What is the difference between the critical path method and other methodologies?

In case this wasn’t implicitly clear, we should explicitly state that the critical path method is not a project management methodology .

Therefore, comparing it to other project management methodologies or even Agile frameworks — like Waterfall , Kanban , or Scrum — would be equivalent to comparing ducks to duct tape.

Instead, it helps to think of CPM as one of the many project management tools within your arsenal. Just like you can use a task management platform like Plaky to keep track of progress and productivity, you can use CPM to chart out a project schedule. 

This also means you are free to use CPM regardless of which PM methodology you decide to follow, so long as the methodology in question doesn’t resist this kind of thorough preplanning. For example, Agile methodologies and CPM typically don’t mesh well because CPM requires you to have all project tasks mapped out from the get-go.

That being said, we certainly can compare the critical path method to other similar project management tools.

Given that CPM is a scheduling tool, the most immediate and most relevant comparisons can be drawn between it, PERT , and Gantt charts .

Critical path method vs PERT

PERT (Program Evaluation Review Technique) and CPM share a lot in common.

Not only are they both scheduling tools, but they were also developed around the same time.

Back when CPM was being developed at DuPont, the US Navy’s Polaris Project was also behind schedule.

PERT was the solution they developed to combat this issue.

Needless to say, it operated a bit differently.

Much like CPM, PERT requires you to break the project down into bite-sized tasks and map out the necessary sequence of tasks based on their dependencies. 

Unlike PERT, however, it provides some guidelines on how to estimate the duration of each task.

This is done by assigning each task 3 potential durations:

• The most optimistic (O) time needed to complete each task,
• The most probable (M) time needed to complete each task, and
• The most pessimistic (P) time needed to complete each task.

Once you have this data, you can calculate the PERT estimate (E) using the following equation:

E = (O + 4M + P) / 6  

In addition to this, charting out the timeline using PERT means starting from the deadline and working your way backward.

Critical path method vs Gantt chart

Gantt charts are bar charts used to visualize a project’s schedule.

Perhaps the most widely used scheduling tool today, Gantt charts were developed around the time of the First World War by Henry Gantt, who used them to measure the productivity of his employees. 

It didn’t take long for the US military to take notice of these charts and start implementing them in their operations.

Just like CPM, Gantt charts are used to visualize the flow of a project and link dependencies.

However, they don’t feature a system for calculating task durations.

In other words, once you already know how long each task will (or should) take, you can use Gantt charts to manage the project to great effect.

But you have to use another tool to calculate or estimate the task durations.

In this way, Gantt charts are compatible with CPM and PERT.

You can use the latter tools to map out the duration of a project with all its tasks and then use a Gantt chart to keep track of everything once the project gets underway. 

Doing this with CPM will also let you spot if the same person is assigned multiple tasks at the same time, thereby helping you avoid one drawback of using CPM.

Critical path method terminology

To those who have never used CPM, a critical path diagram will seem like some form of Elvish they can’t read.

But don’t let this dissuade you from using it. 

The truth of the matter is that the only math involved in CPM is simple addition and subtraction. Most projects also measure task duration in days, removing the need to fiddle with hours and minutes.

In other words, the math required for calculating the critical path method couldn’t be simpler.

But to do these calculations, you first need to get acquainted with CPM’s acronym-heavy terminology . 

So, let’s quickly explain the following CPM terms:

• Critical path,
• Activity nodes,
• Early start time (ES),
• Early finish time (EF),
• Late finish time (LS),
• Late start time (LF),
• Total float/slack (TF), and
• Free float (FF).

Term #1: Critical path

The critical path is the sequence of dependent activities with the longest overall duration.

In the diagram above, the C1-C2-C3 string of activities constitutes the critical path , as they take 30 days to complete.

The alternative routes — consisting of activities A1-A2-A3 OR B1-B2-B3 — take only 27 days and 12 days to complete respectively. 

In other words, no matter how quickly you go through these secondary routes, the project won’t be completed until the activities on the critical path get done. Even if activities B1, B2, and B3 took twice as long to complete, they wouldn’t impact the deadline at all.

Term #2: Activity nodes

Activity nodes are rectangles used in CPM diagrams designed to hold all the crucial information needed for charting a project’s critical path.

Once upon a time, CPM was performed using the so-called activity-on-arrow diagrams . These diagrams contained much of the same information but were more visually confusing.

Nowadays, activity-on-node diagrams are more popular. As the more intuitive method, this is the only type of diagram we’ve used in this guide.

Each task required for project completion gets its own activity node. The illustration above features 9 activity nodes: A1, A2, A3, B1, B2, B3, C1, C2, and C3. 

These nodes are then linked with arrows to point out task dependencies — you can’t begin work on A2 before you’ve completed task A1 .

In addition to the activity name, the node also contains all the following data found in the picture below.

Term #3: Early start time (ES)

Early start time denotes the earliest possible point at which you can start working on a task . 

The ES for the first task(s) in a project is set to 0. 

To calculate the ES for all other tasks, just copy the EF (early finish time) of the preceding dependent task. If a task is dependent on 2 or more previous activities, refer to the activity with the longer ES.

In case this sounds confusing, let’s apply the principle to the simplest activity imaginable — making tea. 

You want to make a cup of tea, but all your teacups are dirty. 

Making tea depends on 2 tasks — boiling water and washing a teacup. 

The water takes 5 minutes to boil, but you can wash a cup in 30 seconds. You can do these activities at the same time, but the earliest time at which you’ll be able to make tea corresponds to when you finish the longer of the dependent tasks. 

In this example, making tea has an ES of 5 minutes — because this is the time of the longer of the dependent tasks.

Term #4: Duration (Dur)

Duration is self-explanatory — it denotes how long you expect a task will take to complete.

Term #5: Early finish time (EF)

Early finish time denotes the earliest moment at which it is possible to finish a task . 

To calculate the early finish time for a task, you take its ES and add the task duration (Dur).

Since the first activity in a project generally has an ES of 0, the EF will be identical to the duration of the first activity.

All dependent tasks that follow immediately after it will take the first task’s EF as their ES, and add their duration to it to calculate their EF.

Term #6: Late finish time (LF)

Late finish time denotes the latest point at which you can complete an activity without it prolonging the overall project timeline .

Tasks that are on the critical path have identical LF and EF values. 

To calculate the LF of tasks that aren’t on the critical path, you have to start with the project completion node and work your way backward. The LF of a node is equal to the LS (late start time) of its subsequent dependent node.  

This is another equation that looks way more complicated in isolation, so let’s simplify it using the previous tea-making example. 

The final activity (making the tea) has an LS of 5 minutes. This is the LF value of all activities that lead into it. So, both washing the cup and boiling the water have an LF value of 5 minutes.

Term #7: Late start time (LS)

Late start time denotes the latest point at which you can start work on an activity without having it prolong the overall project timeline .

To calculate the LS of an activity, use the following formula:

LS = LF – Dur 

In our example, washing the cup takes 30 seconds. This activity has an LF of 5 minutes. Therefore, its LS equals 4 minutes and 30 seconds. 

In other words, if you start washing the cup at the 4-minute and 30-second mark, you’ll still be able to start making tea on schedule. 

Any later than that, and your boiling water will be waiting for you to finish washing the teacup, thereby extending your afternoon-tea timeline.

Term #8: Total float/slack (TF)

Total float and total slack denote the amount of wiggle room you have before you must start working on tasks that are not on the critical path.

Float and slack are synonymous, the only difference between the two lies in your attitude — float is how much extra time you can dedicate to tasks whereas slack is how long you can procrastinate.

They’re even calculated using the same formula. 

To calculate total float/slack , use either of the following formulas:

TF = LF – EF

TF = LS – ES

In the tea-making example, boiling the water has no float since it’s on the critical path.

Washing the cup has a total float of 4 minutes and 30 seconds.

Term #9: Free float (FF)

Free float is the same as total float — it even uses the same formula. 

The difference between them is entirely contextual. 

When we have several non-critical path tasks chained together, the backward pass calculations show that they all have the same float. 

But if you extend one of those tasks by any amount, you’ll reduce the remaining float of subsequent tasks in that chain. 

However, you’ll sometimes run into non-critical path tasks that aren’t part of an expanded chain of non-critical path tasks. We say that those tasks have free float because using up their float won’t reduce the float of any subsequent activity.

For example, if we had just one task labeled A instead of the task chain A1-A2-A3, then A would have free float.

📖 Now that you understand how the Critical Path Method works, dive further into the subject of project management — explore our Project Management Glossary of Terms .

Use the right tool for the job — try Plaky for free

The critical path method is a superb tool for project planning, but things rarely go according to plan. To ensure your project stays on schedule, you need to be able to track progress accurately and adapt to changing situations.

This is where specialized project management software such as Plaky comes in. Among other things, Plaky allows you to:

• Have all your project and task information in one place,
• Use Gantt charts to visualize the schedule and adapt to changes easily,
• Have insight into all project activities,
• Automatically calculate costs, 
• Set projects up using versatile project templates , and more.

If you’d like to try out the app for yourself, you can create a free Plaky account today and test out the full feature set for 14 days — no strings attached!

• Accettura, A., Bergsma, K., Boszak, T., Callaway, J. L., Cote, N., Doepker, C. Harbidge, M., Her, S., Hlushko, T., Holmes, J., Knight, M., MacDowell,  P., Marshall, C., McDougall, L., Prima, A., & Story, T. (2021). Project Management for Instructional Designers, First Canadian Edition. Retrieved from http://pm4id.ca. Licensed under a Creative Commons Attribution NonCommercial ShareAlike (BY-NC-SA) license.
• Arun, R. (2021, October 14). Everything You Need To Know About CPM: The Critical Path Method . https://www.simplilearn.com/tutorials/project-management-tutorial/critical-path-method
• Kent, R. (2017). Quality Management in Plastics Processing . William Andrew Publishing. https://www.sciencedirect.com/topics/engineering/arrow-diagram
• Levy, F. K., Thompson, L. G., & Wiest, J. D. (1963). The ABCs of the Critical Path Method . Harvard Business Review. https://hbr.org/1963/09/the-abcs-of-the-critical-path-method
• Wallace, C. (2017, December 31). This Project Management Technique Is More Than A Productivity Hack . Forbes. https://www.forbes.com/sites/christinawallace/2017/12/31/no-more-productivity-hacks-2018/

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CPM in Project Management: Understanding Critical Path Method

• February 10, 2024

Project management has been a key aspect of many industries worldwide, playing an essential role in ensuring the smooth execution of tasks, from project initiation to completion. It involves planning, organizing, and administering the resources and tasks necessary to achieve specific business goals . As businesses grow and projects become more complex, the need for effective project management strategies has become increasingly focused in many organizations.

The Critical Path Method, often abbreviated as CPM, is one of the valuable tools utilized in project management. It found its roots in the late 1950s, developed as a joint venture between DuPont and Remington Rand Corporation for managing plant maintenance projects. From those industrial beginnings, CPM has today spread across various sectors. It is a methodology that, when properly understood, can significantly improve productivity and efficiency in a multitude of project types.

This blog aims to provide a comprehensive understanding of CPM, its application in project management, its benefits, and potential hurdles that may be encountered during its implementation. Throughout the post, you will also encounter key components and principles related to project management and the role of project scheduling, particularly using CPM. By the end of the article, you will have a thorough understanding of the CPM’s meaning in project management and how it can influence project success.

Understanding Project Management

Project management is pivotal to the success of any business. It guides progress from conception to completion, dictates the use of resources, coordinates personnel, and most importantly, manages time. Essentially, project management is a process encompassing planning, organizing, motivating, and controlling resources to accomplish specific goals within a group or organization. Its significance is tremendous, as it sets an organization’s strategic alignment, provides leadership and direction, and assures better resource control.

Project management consists of several critical components. These include the project scope, which defines project goals, cost and time management, overseeing the budget and schedule respectively, quality management that ensures the results align with established standards, and risk management which prepares for and mitigates unforeseen circumstances. These interconnected components are crucial for the successful completion of any project. It is particularly essential for a project manager to master these components, given their broad responsibilities in all these areas.

The project manager’s role is central in any endeavor. Entrusted with the overall project, they plan, execute, monitor, control, and conclude projects. They are responsible for coordinating teams, managing resources, and ensuring the project stays within the set timeline, scope, and budget. Apart from these tasks, project scheduling is one vital duty of a project manager, serving as an important tool in project management.

Project scheduling represents the mechanism that transforms project action plans into a functioning timetable. It functions as a framework to plan, coordinate, and track specific tasks and milestones within a project . Given the enormous role that project scheduling plays in project management, several methods have been developed to improve its effectiveness. One of these methods, which this post focuses on, is the Critical Path Method (CPM). Let’s examine the meaning of CPM in the context of project management.

Comprehensive Overview of Critical Path Method

The Critical Path Method, commonly abbreviated as CPM, is a process employed in project management to identify important tasks and schedule them to reduce the risk of procrastination. The CPM was first conceived in the late 1950s by James E. Kelley of Remington Rand and Morgan R. Walker of DuPont. Their methodology for scheduling projects was an essential part of the technological advancements that have shaped today’s modern project management practices. The evolutionary development of CPM has significantly influenced how project management is conducted today, offering a systematic approach to managing a variety of tasks.

Understanding the principles that govern the Critical Path Method is key to leveraging its benefits. The principal theory behind CPM is that there are some tasks in a project that can be delayed without pushing the project off schedule. These tasks are referred to as “slack tasks.” Conversely, there are tasks that cannot be delayed, as they have a direct impact on the project deadline. These are known as “critical tasks,” and they form the critical path in the project schedule. The CPM aims to identify these critical tasks and ensure they are completed on time.

The Critical Path Method is not only crucial for managing deadlines but also for efficiently allocating resources and mitigating project risks. The value that CPM brings to project management is immense. It allows for better organization and allocation of resources, ensures timely completion of projects, and ultimately, boosts productivity. Also, with the proper application of CPM, project managers can effectively predict potential issues and provide proactive solutions, thereby ensuring smoother project execution.

In fact, the use of CPM in project management has become a standard practice in many industries. It’s important to understand that the method is not exclusive to large-scale projects; even smaller projects can benefit from the application of CPM. It’s also not limited to certain types of industries or projects. Whether it’s software development, construction, event planning, or any other project management intensive field, the application of CPM can streamline processes significantly. However, understanding the intricacies of the method and appropriately applying it are essential for reaping its benefits.

Application of CPM in Project Management

The Critical Path Method (CPM) holds immense potential in project management, particularly in the aspect of scheduling. The CPM process begins with listing all the tasks or activities required to complete the project, along with their estimated durations. The relationships between these tasks, or which tasks must be completed before others can begin, are then established. These are often referred to as dependencies within project management . Next, a project network diagram is drawn that connects all the tasks. The critical path is then identified as the longest path through the network, representing the minimum time to complete the project. By focusing on the tasks in the critical path, project managers can better oversee and control project timelines.

But how does one create a CPM diagram? The process begins with graphically laying out the entire project with nodes representing the tasks, and lines to showcase relationships and sequence among them. Each path through the project is then analyzed for its total duration, with the longest one being the critical path. The “float” or “slack” time for non-critical tasks – that is, the amount of time you can delay a task without it causing a delay in the project, is also calculated. Monitoring these critical and non-critical tasks forms the real management value of CPM.

Let’s explore some practical examples of how CPM is used in project management. In construction projects, the CPM could depict tasks from laying the groundwork and putting up structural elements, to installing wiring and painting walls. In software development, stages might include initial concept, programming, testing, and launch. For events like conferences, tasks could range from booking venues and sending invitations to arranging speakers and catering. In each case, the CPM identifies the sequence of tasks, estimates timelines, and highlights the “make-or-break” tasks on which the project’s deadline depends.

Lastly, it’s worth mentioning that while the traditional way of doing a CPM diagram is through pen and paper, project management systems such as MS Project and Primavera are now widely used for precision and convenience. These tools provide the ability to create CPM diagrams, auto calculate critical path and slack time, and enable changes with automatic recalculations. This largely helps to eliminate potential errors, save time, and better manage the overall project schedule.

Possible Challenges and Solutions in CPM Implementation

Implementing the Critical Path Method (CPM) in project management is not without its potential hurdles. Misinterpretation of the project’s scope, overstocking resources, and the inability to visualize the overall project timeline can become significant challenges when implementing CPM . Also, relying solely on CPM without considering other project management methodologies and ignoring risk management can lead to project failure. Therefore, a balanced and calculated approach is vital when utilizing CPM for project management.

Addressing these challenges involves several practical solutions and meticulous strategies. First and foremost, a thorough understanding of the project scope is imperative. This understanding forms the basis for the effective usage of the CPM methodology. Proper allocation and distribution of resources over the project’s timeline is another critical step in mitigating these hurdles. Regular project reviews can help in identifying any failures before they escalate further. Lastly, embracing the hybrid approach, which involves incorporating different project management methods along with CPM, can bring about a more holistic approach to managing projects.

Technology has advanced to the point where incorporating it into complex methodologies like the Critical Path Method in project management has become less of an option and more of a necessity. A myriad of software tools are now available that assist in efficient CPM implementation. These tools provide visual aids to simulate the project timeline better, thereby making the process more understandable and manageable. Furthermore, they offer features to keep track of the project, allocate resources efficiently, deal with risk management, and create “what if” scenarios, making them invaluable assets when implementing CPM. Ultimately, the usage of such tools enhances the overall efficiency and effectiveness of the project, leading to a successful and timely execution.

Wrapping up our discussion, let’s revisit the key points about CPM (Critical Path Method) elucidated throughout the article. Our journey embarked from the basics of project management with a particular emphasis on the process of project scheduling. We gradually delved deeper, shedding light on the concept of CPM, its history, principles, and benefits for project management. We underscored how the CPM operates optimally in the arena of project scheduling and also explained the steps to create a CPM diagram.

Like the dual sides of a coin, we did not abstain from highlighting the potential challenges encountered while implementing CPM. Despite its benefits, the adoption and utilization of CPM are not always devoid of obstacles. Some of the areas that might present issues include understanding the complexity of the processes, data quantity and quality, and time constraints, among others. Yet, we proposed practical solutions to these challenges, emphasizing the key role of continual learning, meticulous planning, effective communication, and team flexibility.

Further, we introduced the use of software tools in CPM implementation. The benefits of using technology for CPM implementation include improved accuracy, effective collaboration, and time-saving. Certain software tools can automate the challenging task of continuously creating and updating CPM diagrams, freeing project managers to focus more on overall strategy and decision-making.

In summary, despite its challenges, CPM remains a potent tool in the project management field, primarily for project scheduling. It aids in identifying the longest and most consequential path in a project and provides the flexibility to control and adjust the project schedule as per evolving circumstances. CPM also encourages Project Managers to enhance their skills by managing their projects more efficiently. Adopting CPM in your project management approach could undoubtedly boost the productivity and efficiency of your projects. Embrace it and let your projects witness the power of optimal scheduling and resource allocation.

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Critical Path Method for Project Management

September 2, 2023 - 10 min read

The Critical Path Method (CPM) is a vital project management tool that represents the most extended sequence of tasks that must be accomplished to ensure the completion of the entire project.

You can determine the critical path by measuring the longest sequence of dependent activities from start to end.

It can be visually represented by using a Gantt Chart software that can help build a visual timeline of the project.

In this article, we’ll detail in depth the steps for using critical path method for project management, explain how to calculate the length of your project, explain how keeping an up-to-date project schedule allows you to have flexibility within your critical path, and share our helpful project scheduling template to get you started.

What is the critical path method?

The CPM is a sophisticated project management technique to plan, schedule, and manage complex projects. It involves identifying all the tasks needed to complete a project, determining the sequence in which these tasks must be carried out, and then calculating the most prolonged duration of time it will take to complete the project from start to finish. This most prolonged duration is known as the ‘critical path,’ and it provides a clear timeline for project completion.

In CPM, tasks are categorized as ‘critical’ and ‘non-critical.’ Critical tasks must be completed on time to ensure the project is finished on schedule. Any delay in a crucial task will result in a delay in the project. Non-critical tasks, on the other hand, have some flexibility in their scheduling so they’re less likely to cause a delay in the project completion.

CPM is especially valuable for projects with numerous interdependent activities, as it allows project managers to see where potential bottlenecks may occur and where resources can be allocated most effectively. By identifying the critical path, project managers can prioritize tasks, mitigate risks, and better ensure timely project completion.

Benefits of using critical path method in project management

CPM offers many benefits that can significantly enhance the effectiveness of project management. 

• Provide a clear visualization of the project timeline. By illustrating the sequence and duration of each task, CPM allows project managers to gain a comprehensive understanding of the project’s flow, making it easier to plan and manage resources effectively.
• CPM’s ability to identify critical tasks. This not only helps in prioritizing tasks but also allows for the proactive management of potential delays. By understanding which jobs have the flexibility to be delayed without affecting the overall timeline, project managers can better manage changes or issues that arise during the project life cycle.
• CPM aids in risk identification and mitigation. Highlighting the critical path allows project managers to foresee potential bottlenecks or delays and proactively mitigate these risks. This can lead to a significant reduction in project downtime and associated costs.
• CPM promotes better communication within the project team. With a clear visual representation of the project’s timeline, team members can better understand their roles, responsibilities, and the impact of their tasks on the overall project. This can lead to improved collaboration, efficiency, and overall project success.

In summary, the CPM is an indispensable tool in project management, offering enhanced planning, risk mitigation, resource management, and team collaboration capabilities.

How to find the critical path in a project

Step 1: Identify all tasks required to complete the project

Start by listing all the functions or activities that need to be completed for the project’s successful conclusion, also known as a work breakdown structure . When created thoroughly, the work breakdown structure is a roadmap that guides a team when completing projects — whether simple or complex. Here’s a powerful work breakdown structure example from Wrike.

Step 2: Determine the sequence of tasks

Next, identify the order in which the tasks need to be performed. Some tasks may depend on the completion of others before they can begin, while others may be carried out concurrently. This step is crucial in understanding the dependencies and relationships between tasks.

Step 3: Estimate the duration of each task

Assign a time estimate to each task. This should be the total time required to complete each task from start to finish. Make sure to account for any potential delays or issues that may arise.

Step 4: Draw a network diagram

Using the information from the previous steps, draw a network diagram. This visual representation should depict all the tasks, their sequence, and their dependencies. Each task is represented as a node on the diagram, and the arrows between nodes represent the dependencies between tasks.

Step 5: Identify the critical path

The critical path is the longest path from the start to the end of the project, passing through all the essential tasks to the project’s completion. In other words, the sequence of tasks determines the minimum time needed to complete the project. On your network diagram, the critical path is the longest from the initial to the final task.

Step 6: Calculate the float

The float or slack is how long you can delay a task without waiting for the project. Tasks on the critical path will have zero float, meaning they can only be postponed without impacting the project timeline. However, non-crucial tasks may have some float, allowing for some flexibility in scheduling.

Step 7: Monitor the critical path

Once the project is underway, closely monitoring the tasks on the critical path is essential. Any delays in these tasks will directly impact the project timeline. Regularly updating and reviewing the critical way can help identify potential issues early and keep the project on track.

Consider using Wrike’s critical path method template to augment this process further. This pre-structured template simplifies identifying your project’s critical path, saving time and enhancing project planning efficiency. 

Try our template

Critical path method example

Now we’ll try to demonstrate the concept of the critical path method with a simple, real-life example: planning a killer party. How should you plan and execute this project?

1. Define the project scope

First, we need to define all of the tasks that must be finished to complete the project. For our party example, it might look like this:

• Choose a date and venue
• Make the ultimate playlist
• Set up the sound system
• Invite your friends
• Buy the food and drinks
• Cook your famous casserole
• Host the party

When we look at these tasks individually, we realize that some of them cannot be started before the others are completed. That is, some tasks are dependent on others. We’ve designated these relationships in the table below:

The actions “invite your friends,” “buy the food and drinks,” “cook your casserole,” and “host the party” form a sequence of tasks that must be performed in a specific order, one right after the other, to ensure a successful result. Such tasks are called sequential activities.

Together with the start of our project (“choose a date and venue”), these tasks are the most critical steps in completing our project. Thus, these actions will be placed on the critical path.

2. Define different project paths

You can have more than one critical path in a project so that several paths run concurrently. This can result from multiple dependencies between tasks or separate sequences that run for the same duration.

In planning a party, various project paths will consist of tasks that need to be completed. For example, one path could involve tasks related to booking the venue, such as researching options, visiting potential locations, and finalizing the booking. Another path might focus on the catering, which includes deciding the menu, finding a caterer, and arranging the food and drink delivery. Another path could be about entertainment, involving tasks like hiring a DJ or band and planning games or activities.

While separate, each of these paths is an integral part of the overall project and must be coordinated effectively to ensure a successful party. By clearly defining these different project paths, you can better manage the tasks and timelines associated with each one.

3. Consider the resource constraints

Traditional critical path schedules in project management are based only on causal dependencies. We’ve already marked these dependencies in our plan. (e.g., it’s impossible to cook the casserole without buying the ingredients). However, a project may have limited resources that need to be taken into consideration, such as how to calculate load in resource planning. These limitations will create more dependencies, often referred to as resource constraints .

If you work on a team, you may split the project work between team members. In our example, while you’re choosing a date and venue and inviting people, one of your friends can make a playlist, and another can get the food and drinks. The tasks can be done in parallel, as in our chart above.

However, if you’re the only person responsible for the project, you have a resource constraint because you can’t be in two places at the same time. In this case, your critical path will look different.

On the chart above, we assume you first need to choose the date and venue, and only later can you make a playlist. However, depending on the project conditions, these tasks can be performed in a different order.

4. Calculate the length of your project

L et’s assume you have to do everything by yourself. We estimated the length of time each activity will take. Also, we determined the approximate start time for each task on the critical path. Here’s what we came up with:

Now, if we add up all of our critical tasks’ duration, we’ll get the approximate time we need to complete the whole project. In our case, three days and six hours, since “make the ultimate playlist” and “set up the sound system” are not on the critical path. If we add the duration to the start time, we can calculate the earliest project completion time. Understanding the CPM allows us to make this calculation quickly and accurately.

5. Leave space for flexibility

The critical path method was developed for complex but fairly predictable projects. However, in real life, we rarely get to manage such projects. Let’s say you plan to redecorate your living room with a friend.

Your task list may look like this:

• Get rid of the old furniture
• Paint the walls
• Fix the ceiling
• Install the new furniture

Your friend’s responsibilities are to:

• Choose the new curtains
• Hang the new curtains

T he curtain tasks form a sub-project and can be treated as a non-critical path. Your friend can “choose the new curtains” and “hang the new curtains” any time before the end of your project. The curtain tasks have flexibility in the start and end date, considered float. These tasks are parallel and will not be placed on the critical path. Here’s how this project would look on a Gantt chart :

If any of the parallel tasks were to be significantly delayed, it would prevent our whole project from being completed on time. Therefore, you should always keep an eye on similar tasks.

6. Adjust to the changes in the critical path

Let’s assume that choosing the curtains took our friend longer than we initially expected. This will delay the end of the project.

Our redecoration is incomplete without the new curtains, so the path that previously was non-critical becomes critical. The initial critical path changes.

To monitor your non-critical tasks, your project schedule must be current. That’s the only way you’ll know exactly where your project is at any given moment and whether it will be delivered as initially planned.

Critical path method vs. PERT

In project management, the CPM and the Program Evaluation and Review Technique (PERT) are valuable tools. However, they each have distinct characteristics and are better suited to different types of projects.

CPM is a deterministic approach that assumes a fixed time frame for each task. This makes it ideal for projects with well-known task durations and little variability, like construction or manufacturing projects. CPM focuses on the critical path, the sequence of tasks that determines the project’s shortest duration. By identifying this path, CPM allows project managers to prioritize tasks directly impacting the project’s timeline.

PERT is similar to the critical path in that they are both used to visualize the timeline and the work that must be done for a project. However, with PERT, you create three different time estimates for the project:

• The shortest possible amount of time each task will take
• The most probable amount of time
• The most extended amount of time tasks might take if things don't go as planned

This makes PERT ideal for research and development projects or any other project with uncertain task durations. While both methods help in project planning and scheduling, PERT’s ability to handle uncertainty makes it more flexible in the face of potential changes or delays. CPM’s focus on the critical path can make managing and controlling tasks critical to the project’s timeline easier.

The choice between CPM and PERT should be based on the nature of your project and the level of certainty or uncertainty in task durations. Both methods offer valuable insights that can help drive project success.

CPM success story

The Hoover Dam , constructed between 1931 and 1936, is a testament to effective project management’s power. While the critical path method hadn’t been formally defined yet, its principles were applied during the dam’s construction. 

The project had many activities, each with dependencies and timelines. The project managers had to coordinate these activities in such a way as to ensure the project was completed on time and within budget. They effectively identified the project’s critical path, focusing resources and attention on the tasks that would cause the most significant delays if not completed on time.

The Hoover Dam was completed two years ahead of schedule despite the project’s complexity. This early completion was primarily due to the effective use of what we now know as the critical path method, making it a compelling case study for successfully implementing this technique. 

This case study provides a practical example of the critical path method in action and illustrates its potential in managing large-scale, complex projects.

How Wrike can help you with your critical path management

Determining the critical path of a project isn’t exactly a quick process. That’s why we’ve designed a pre-built template for project scheduling that will help you progress through the steps of creating your critical path. Our project scheduling template allows our customers to visualize the critical path on a Gantt chart, assign tasks to team members, and drag and drop activities to ensure proper resource management. 

Ready to use Wrike for your critical path analysis?

Further reading:

Here are some further resources you can use to brush up on your critical path method knowledge:

• The Critical Path Method , Seminar, Stanford
• Explaining the Critical Path Method , U.S. Department of Health and Human Services
• The ABCs of the Critical Path Method by Harvard Business Review

How to Use a Single Gantt Chart for Multiple Projects

• When to Use a Project Calendar vs. a Gantt Chart

Occasionally we write blog posts where multiple people contribute. Since our idea of having a gladiator arena where contributors would fight to the death to win total authorship wasn’t approved by HR, this was the compromise.

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What It Means to Be a Digital Project Manager

Today's most effective project managers are the ones who have moved their teams and processes online. Using online project management, collaboration software, and cloud file storage systems, work is getting done efficiently and with better results. These digital project managers are the new faces of project management, and if you are looking to dive into the field, you need to start preparing now.

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Master Project Management with the Critical Path Method

Project management requires a wide spectrum of skills , organizational abilities, and attention to detail to make sure everything moves forward according to plan. A good project manager is able to keep all the plates spinning in sync while making it appear effortless at the same time.

However, the more plates you have spinning at once, the harder this is to accomplish. Critical path method (CPM) is one of the tools project managers can use to create a comprehensive plan and organize complex projects with many moving parts.

In this Process Street post, I’ll take you through the CPM process step-by-step, and then show you how our templates and checklists can take some of the stress out of your project management.

Read on, or feel free to skip ahead:

Project management 101

What is critical path method, steps to effectively (and easily) use the critical path method, project management with process street.

Let’s jump in!

To begin with, let’s do a quick overview of what project management actually involves. There are generally considered to be five stages of project management that will guide the product development process for businesses.

Stage 1: Concept

The first part of this stage is generating ideas. These ideas can come from anywhere – employees, customers, competitors, media – but it’s important to then screen your ideas for the most viable options. You’ll also want to do some preliminary research on whether or not your idea is actually feasible. There’s no point in planning out a project you won’t have the resources to complete.

Some questions to consider when vetting your ideas would be:

• Is this a short- or long-term project?
• Is the project too ambitious, or not ambitious enough?
• What are the risks associated with the project?
• Do we have the experience to complete the project?
• Do we have the resources to complete the project (time, labor, materials, funds, etc.)?
• Is the project unique/have value?
• What outcome do we expect by completing this project?

These basic questions will help guide you through choosing the best ideas for your organization and setting realistic expectations. In developing your intial concept, you may realize it’s more beneficial to start out with a smaller, simpler version and add additional features later. You may also discover that your favorite idea has already been done by a competitor, or won’t provide value for your customers.

Many projects can end up scrapped in the very beginning (read this guide on getting your proposal approved!), but for those that proceed to the planning stage, this is where the project management strategy first comes into play.

Stage 2: Plan

Once you’ve settled on an idea, you now need to come up with a strategy for completing it. Stage 2 is where you’ll set your goals and outline the scope of your project. You may already have an established process for creating your project timelines, but if not, there are two popular methods to consider.

“The trouble with not having a goal is that you can spend your life running up and down the field and never score.” – Bill Copeland , poet

The first method is called S.M.A.R.T. George T. Doran developed S.M.A.R.T. in 1981 to make goal-setting more practical. Since then, it’s been widely adopted across various industries, and even featured in Peter Drucker’s Management by Objectives.

S.M.A.R.T. breaks setting goals into five core steps:

• Specific: Who, what, where, when, which, and why
• Measurable: Criteria to determine goal success
• Attainable: Identify most important goals and how to achieve them
• Realistic: Understand what it’ll take to reach your goals
• Timely: Create a time frame for achieving the goals

For most of this post, I draw on the example of publishing a blog post, so let’s see how we could apply the S.M.A.R.T. method to creating goals for that project.

Overall S.M.A.R.T. goal: Publish a post that increases blog traffic by 20% by the end of the year.

• Specific: Writers will use rigorous research practices and SEO optimization to create content that is accurate, actionable, and accessible.
• Measurable: Site analytics will show a 5% increase in reading time by the end of the quarter.
• Achievable: Each content writer will create at least one deep-dive post a month in order to provide more substantive content.
• Relevant: Our aim is to be the best at providing our readers with interesting and informative content.
• Timely: Each quarter, we’ll review site analytics to ensure 5% growth, and adjust accordingly if not, so we meet 20% growth by end of year.

Here we can clearly see how the S.M.A.R.T. method has enabled us to set a precise goal and detail how we plan to achieve it. If we’d said our goal was: increase blog traffic this year instead, it’s likely we wouldn’t meet that goal in the end. Goals that are vague without a strategy for completing them are inherently more difficult to complete.

Some have argued, however, that the S.M.A.R.T. method hasn’t been able to keep up with the agile-centric environments of modern organizations. Adam Kreek is one such person. Kreek is an entrepreneur, motivational speaker, and Olympic gold medalist, so he knows a thing or two about setting goals.

“When we prepared for our Atlantic crossing, our higher goal was to cross the Atlantic Ocean, but we also created three rules to support that higher goal. The first rule was don’t die, the second rule was don’t kill your mates, and the third was don’t sink your boat. So look after yourself, look after each other, and look after your equipment.” – Adam Kreek

Drawing on those three rules, Kreek developed C.L.E.A.R. in an attempt to foster collaboration and unity rather than division among your team. C.L.E.A.R. stands for:

• Collaborative: Goals should encourage team collaboration.
• Limited: Make sure to keep scope manageable.
• Emotional: Tap into team passions to maximize productivity.
• Appreciable: Break tasks into the smallest possible steps that feel achievable.
• Refinable: Stay flexible and adjust as needed.

Applying the C.L.E.A.R. method to our blog post example would look like this:

• Collaborative: We will implement a peer review process to verify content quality.
• Limited: We will monitor read time to identify which topics are of greatest interest.
• Emotional: Writers will be encouraged to pitch their own deep-dive posts.
• Appreciable: We will create a process for blog post production that follows every step of content creation.
• Refinable: We’ll create a Slack channel to address obstacles that come up and adjust as needed.

As you can see, the C.L.E.A.R. method is more adaptable in the moment and involves much more teamwork than the S.M.A.R.T. method. Both, however, have a focus on identifying your goals, the outcome you want, and breaking tasks into the smallest possible steps. The method you choose will depend on your organization and the specific goals you’re focusing on.

The planning stage is when you’ll want to set up communication and risk management plans, but it is also when you lay out the foundation for your critical path method diagram.

Stage 3: Execute

This is the stage where you CPM will really come into play, though. CPM is a crucial tool for project managers because it will make sure the project kicks off on the right foot. CPM’s algorithms enable you to accurately predict how long the project will take, and what resources you’ll need to do so, which means you’ll be able to deliver more accurate projections while completing the project.

Stage 4: Monitor

Anything can go wrong at any time, so you’ll want to pay close attention to how the project is progressing. CPM will identify any time cushions you have in your project timeline and will assist in monitoring performance and progress.

As I’ll cover a little further down, though, CPM is not a perfect system, so close monitoring will be vital for successful completion.

Stage 5: Close

Once the project is completed, all that’s left to do is wrap up any loose ends, evaluate how well the process and budget were followed, and file your final report.

Now that we’ve done a quick review of project management, let’s look at how CPM fits into these stages.

Critical path method is a technique used to model the essential factors involved in your project. Your project model should include:

• Tasks required for completion;
• Time estimates for each task;
• Any dependencies between tasks;
• Expected milestones or deliverables;
• Any hard deadlines already set.

With this information, you can calculate the critical path by adding together the durations of each dependent task (i.e. any task that can’t be completed until the previous one has been finished).

Once the critical path has been calculated, you’ll be able to forecast the project’s optimal timeline for completion and better prioritize tasks and resources .

Benefits of using critical path method

Critical path method is a vital tool when it comes to project planning, scheduling, and monitoring. CPM creates a visual model of the project, which makes it easier to identify task dependencies.

By identifying these dependencies, you’re able to plan for contingencies, locate critical tasks, and manage your workflow to keep the project on track. Knowing all of these things enables you to provide more accurate data to your clients or stakeholders, and ensure you always meet your deadlines on time.

Critical path method’s flaws

You do need to keep in mind that CPM is not a perfect system. While CPM is a great planning tool, it operates on the assumption that all the necessary resources are available and doesn’t take into consideration any resource dependencies .

There is also potential for non-critical tasks to be given less attention than they require, in which case they may become critical activities that halt project progression.

As project manager, you’ll need to continuously monitor your project model for any changes and developments that may happen. Not every situation can be predicted or planned for, of course, but using the CPM will help you react promptly if the absolute unexpected does happen.

Let’s go through a practical example to see CPM at work.

CPM involves a lot of math. As a result, I’m going to walk through the stages in two parts.

The first run-through will be the simple, basic, no calculator required outline of each step of the CPM. This is the version you want to look at first if, like me, math is the absolute bane of your existence (writing this post was so fun ).

If, however, you are a whiz with the numbers and are prepared to get down to business, feel free to skip ahead to the algorithms in the next section.

Let’s do this!

CPM: sans math

The first step of any project is to figure out what your result should be and how you plan to achieve that.

What tasks need to be completed? We’re finally writing that blog post. This project will only have two paths to take into consideration, but projects can have any number of critical paths that need to be followed depending on how complex the project is and how many people or departments are involved in completing it.

To define our project’s scope, we first need to list all the tasks needed to complete the project. These are the tasks needed to write and publish a blog post:

• Outline the post
• Request images from designer
• Designer creates images
• Images submitted for approval
• Format the post
• Submit for review
• Make final edits to post
• Make final edits to images
• Add images to post
• Submit for approval
• Publish post

Now we can look at our tasks, determine which order they need to go in, and which tasks are dependent on each other.

Which tasks are dependent on each other? The blog project is actually a collaborative effort between three people: the writer, the designer, and the editor. If we look at the tasks individually, it becomes apparent that some can only be completed after others are finished. (Later on, I’ll explain how stop tasks and approvals in our checklists can automate this process for you.)

For example, the post can’t be submitted for review before it’s written, and the images can’t be designed before they’re requested.

The next step after listing the tasks is to determine which tasks are dependent on each other. The first two tasks ( Outline the post and Request images ) aren’t dependent on any other tasks, and can happen in either order. However, the next two tasks are both dependent are the first two being completed.

You also need to take into consideration how long each task is expected to take. Once you know the task dependencies and task lengths, you’re ready to begin calculating the length of the critical path (the shortest amount of time a project can be completed in).

Early start/finish vs late start/finish The early start, early finish, late start, and late finish will provide the actual time frame you’ll be working with during the project. By calculating these figures you’ll know:

• The earliest possible point each task can be started
• The earliest possible point each task can be completed
• The latest point each task can begin without causing delays
• The latest point each task can end without causing delays
• How much “spare” time you have if a task gets delayed

Once you’ve created a diagram, you can reuse it every time you need to complete a similar project. This is particularly useful – and saves loads of time – when you frequently repeat the same processes or projects – writing blog posts, for instance.

We’ve reached the point now where we need to dive into the numbers.

CPM: for the nerds

I’ve already mentioned some of these terms, but it’s worth reviewing them before we dig in:

• Early start (ES): The early start will always be the first day of your project, because you can’t begin a project before it even starts.
• Early finish (EF): This is the earliest point any uncompleted parts can be finished. This date isn’t fixed; depending on progress and any plan changes, the EF date can also change.
• Late start (LS): The latest point that a task can start without delaying a milestone, usually the project deadline.
• Late finish (LF): This is the latest point a task can be completed without delaying a milestone.
• Forward pass: The calculation of ES and EF for uncompleted tasks.
• Backward pass: The calculation of LS and LF for uncompleted tasks.
• Network diagram: A map of the relationships between project tasks.

With that out of the way, let us begin at the beginning:

Define the project scope First we need to list the tasks required to complete our blog post creation project.

Now that we know what needs to be done, we can begin calculating our critical path.

Analyze and identify the critical path We need to examine our task list and determine which tasks are dependent on each other. For example, the graphic designer can’t create images that haven’t first been requested, and the writer can’t format a post that hasn’t been written yet. You also need to factor in how long each task will take to complete.

In creating a blog post, there are actually two paths involved: the path followed by the writer, and the path followed by the graphic designer. By looking at the task list, we can tell that the writer is responsible for more tasks than the graphic designer. However, it’s not the number of tasks but the duration that will determine which is the critical path.

Our next step is to create a network diagram of each task chronologically in relation to the other tasks. The diagram should look something like the figure below:

In the diagram we can see there are two paths which take approximately the same amount of time:

• A + C + D + E + H + I + J = 13 days duration
• A + B + F + G + I + J = 12 days duration

Path 1 is our critical path because 13 days is the shortest amount of time the project can be completed in.

Having identified our critical path, we need to calculate the total float .

Float, or slack, is your wiggle room. It’s the total amount of time you can spend on a task before it affects your timeline. It’s that perfect little cushion between you and the deadline you’re hurtling toward, so you don’t go splat when you reach it.

There are actually three types of float you need to be aware of:

• Total float: The amount of time a task can be delayed without delaying the finish date.
• Zero float: Every task on the critical path has zero float; there’s no excess time between tasks.
• Negative float: This is the amount of time a project is behind schedule.

The float for the critical path is zero; there’s no wiggle room. If one of the tasks takes longer than estimated, then our project will have negative float , and we may not meet our deadline.

To calculate the float for Path 2, the formula is:

Duration of the critical path – Duration of path “A + B + F + G + I + J”

Using our figures, this translates to:

13 – 12 = 1

The float for Path 2 is 1 day.

Calculate early start & early finish Now that we know what our critical path is, and the path durations, we need to figure out the actual time frame we’re working with – specifically early start/finish and late start/finish .

The calculation for ES and EF is called the forward pass. You need to complete a forward pass for each of the project paths to get an accurate project model.

To calculate the ES and EF of each task, use this formula:

ES = EF of preceding activity + 1 EF = Task duration + ES – 1

Start with the first task of the path; in this case, it is Task A. The first task of a path is always 1.

To get the EF of Task A, the formula would be:

EF = ES + task duration – 1

Task A EF = 1 + 2 – 1 = 2

The ES of Task C (EF of previous task + 1) = 2 + 1 = 3 The EF of Task C (ES of C + duration – 1) = 3 + 2 – 1 = 4

Continue until you have the ES and EF for every task on the network diagram. Make note of the ES in the upper left corner of the task box and the EF in the upper right-hand corner. When you’ve finished, your network diagram should look like this:

*Note: Task I is dependent on two preceding tasks: Task H and Task G. To calculate the ES and EF of Task I, you need to choose the preceding task with the greater EF date.

The EF of Task H is 10 and the EF of Task G is 9. So to find the ES of Task I, we’ll use the EF of Task H.

The formula for ES in this case is: EF of Task H + 1 = ES of Task I

ES of Task I = 10 + 1 = 11

The formula for EF in this case is: ES of Task I + task duration – 1 = EF of Task I

EF of Task I = 11 + 1 – 1 = 11

Calculate late start & late finish With the ES and EF dates out of the way, we need to calculate the late start (LS) and late finish (LF) of each task. The LF of the final task on all paths (Task J) will be the same since the project ends after that task is completed.

This is called the backward pass, because it requires working backwards through the network diagram.

The formulas for LS and LF dates are:

LF of task = LS of successive task – 1 LS of task = LF of task – duration + 1

For the critical path, the LS and LF will be the same as the ES and EF dates.

To complete the backward pass of Path 2, we start with Task G.

The formula to calculate the LF of Task G is: LS of Task I – 1

= 11 – 1 = 10

LS of Task G = LF of Task G – task duration + 1

= 10 – 2 + 1 = 9

Continuing our backward pass, the formulas for Task F would be:

LF: 9 – 1 = 8 LS: 8 – 1 + 1 = 8

With all of your calculations complete, your network diagram should now look like this:

That’s your project model: early start and finish dates, late start and finish dates, and total float. The first time you go through the process for your own project, it may seem complicated and confusing, but with a little practice, you’ll quickly get the hang of it.

And – even better – a good process management application can help you automate the process, so you don’t have to worry about calculation errors or delayed approvals.

Project management is a process that your organization will undoubtedly go through many, many times, whether it’s a relatively simple process like developing an email marketing plan, or something more complex like launching a new product or service.

As with any process, it’s important to first document every step of the process, but also create a structure where that process can evolve as your organization’s needs change.

As I mentioned earlier, the critical path identifies which tasks are dependent on the completion of other tasks. When organizing a team, it can be difficult to ensure that tasks are completed in the correct order.

However, Process Street checklists have that feature built-in. Stop tasks will prevent a particular task from being completed until all previous tasks have been finished. This means you can always be sure that the project progresses in exactly the right order without anything being overlooked or forgotten.

The Approvals feature is also a useful one for project managers to utilize. This feature streamlines the approval process , making handoffs a cinch. Whoever is in charge of making the approval is sent a notification, and can then review and approve the completed work from anywhere using our mobile app.

A free Process Street account allows you to import pre-made templates into your organization, edit templates to meet your needs, or create templates completely from scratch.

Check out this webinar for a more in-depth look at what you can do with Process Street, or dive into our Getting Started with Process Street knowledge base!

Useful templates for project management

• Writing a Proposal: Step-by-Step Guide
• Project Proposal Template Checklist
• Project Management Process Checklist
• Product Launch Checklist
• Project Manager Meeting Planner Checklist

Have you used the critical path method in your project management? Do you have a different approach? Share your experience in the comments!

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Leks Drakos

Leks Drakos, Ph.D. is a rogue academic with a PhD from the University of Kent (Paris and Canterbury). Research interests include HR, DEIA, contemporary culture, post-apocalyptica, and monster studies. Twitter: @leksikality [he/him]

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The Critical Path Method with Example | PMP Notes

When I was preparing for my PMP exam, it was tough for me to understand this CPM concept. I watched tons of videos and read blogs, but nothing was working for me. Eventually, after a hard practice, I cracked the way out.

Today, I am going to discuss the easiest methods to understand concepts. If you are going for a PMP exam , then make sure to draw the network diagram always, as there may be more than one question relating to that network. But if you got a network diagram already in question, you need to visualize and crack the questions.

You may also like PERT & CPM .

Moreover, in a project management life, critical path understanding is the primary area discussed daily, weekly, and monthly meetings. That’s why understanding every concept is quite remarkable.

Let’s see how to get a network diagram from the given table or conditions.

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What is a Critical Path?

How to find critical path, forward pass in cpm, backward pass in cpm, float calculation in cpm, locating the cpm, zero-day start | method, final words, featured posts.

If you see a path met with the below conditions on any network diagram, it is a Critical Path.

• The longest path in the complete network diagram
• The path with the shortest duration to complete a project .

There are some conditions like every activity that should be connected. See if you find if more are mentioned on the given data.

To find a critical path on any project or given conditions, you need to follow the below steps;

Step – 1: Construct a network diagram.

Step – 2: Determine Project Completion time.

Step – 3: Perform Forward and Backword pass (Not necessary every time!)

Step – 4: Calculate the float .

Step – 5: Mark the Critical path with zero float activities.

How to Draw a Network Diagram?

First of all, we need data in tabular form or any proper format;

Now, please read it and see all the conditions to implement during a draw. If you are doing it on plain paper, make sure to use boxed and right angles. This will prevent you from messing around with things and logic.

•  Early Start – ES
• Early Finish – EF

we will get by using  forward pass, and then

• Late  Start – LS
• Late  Finish – LF

we will get by using a backward pass.

Then we will calculate the float that will help to find a critical path.

First of all, I put all the activities as per the given condition on our table. I have also applied the logic, as you can see.

Now, we will calculate the forward pass. for this, you can start with 0 0r 1. There is no condition, but in PMBOK, they took 1. This is logical as my first day on any project should be 1, not 0 days. Still, some school thoughts agree to start with 0. Like they have zero semesters in a college 🙂

I will explain below how I have calculated the forward pass.

From the start, I put 1 and added 7 and then minus one, and hence the formula is like

• Early Start (ES) = Early Finish of predecessor activity + 1
• Early Finish (EF) = Activity Time + Early Start of Activity – 1

I did the same, keeping in view the logic, as shown as per arrowheads. I hope I am clear now. If you feel any nag, comment below, and I am happy to answer.

The next step is to calculate the Backward pass. it is the same as the forwarding pass, but this time we need to keep in view the below formulas;

• Late Start (LS) = Late Finish of Activity – Activity Time + 1
• Late Finish (LF) = Late Start of Successor Activity – 1

This one the most natural part of CPM but the most important one. It helps to locate the critical path in a particular network.

Below are the simple formulas to calculate float;

• Total float for an Activity  = LS of Activity – ES of Activity
• Total float for an Activity  = LF of Activity – LF of Activity

You can apply any, and the answer will be the same. If not, then you are doing something wrong.

It would help if you found all the activities with zero float, or we also call it slack.

In our network diagram, there are different paths like;

• Start – ACF – Finish
• Start – BDEG – Finish
• Start – AEG – Finish
• Start – AEF – Finish
• Start – BDEF – Finish

But we have to look for a path having all the activities with zero float on. In our diagram, Activities BDEF are with zero floats, and hence this is the critical path. This is the longest path, also with 32 days. Rest is less; you can calculate on your own.

That is how you can calculate a critical path. But as I said earlier, you need not go for forwarding and backward path in most of the PMP  exam. Just calculate the longest path from activities durations and check all the possible paths in glace and hopefully, you will get it right, or else you can calculate this method – Practice it hard and let me know in the comments if I can add more on it.

If you belong to other schools of thought, then you will get a final shape like the below picture;

I have explained this with a bit complex diagram so that if you get a hard question, you can still calculate it easily. I got a question to estimate free float and total float on a particular activity, and I just found out that this activity is on a critical path, so I select the answer as zero.

You will get plain paper and a lead pencil during your PMP exam , and make sure to draw boxes for activities and join them with straight and right-angle lines so that you don’t mess up there.

Good Luck! Any questions or you found any mistakes – comment, please.

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1 thought on “The Critical Path Method with Example | PMP Notes”

In the backward pass CPM example here shouldn’t the LS(Activity G) be 28? LF(G) – t(G) + 1 =32-5+1 = 28

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How to calculate the Critical Path with Examples 🥇

The critical path method is one of the most important concepts in project management; however, many students have difficulties in its application. In this post, you will learn how to calculate the critical path of a project step by step by following practical examples.

Before you start we recommend you to review our post how to create a PERT CPM chart step by step with examples ; where we explain how to graphically represent the relationships between the activities of a project. Creating the chart of project is the starting point to calculate our critical path.

You can also check our online critical path method calculator that performs the steps to calculate the critical path automatically.

What is the Critical Path Method?

The Guide for Project Management (better known as PMBOK Guide), defines the critical path as:

“The sequence of scheduled activities that determines the duration of the project”.

To complete a project, we must perform all the activities that compose it. Some activities can be done simultaneously, but others must be done in a certain order. For example, if I am going to build a house, I must first build the walls before painting them. Of all the sequences of activities that make up the project, the sequence that has the longest duration will be the critical path and determines the total project time . As a consequence, the critical path method specifies the algorithm for finding it.

Why is Critical Path Important?

By identifying the critical path, teams recognize the most important tasks to be performed in a project.

Further, any delay in a critical path activity can cause the entire project to be delayed, so managers take extra care to ensure those activities take place as planned.

Important: Projects may have multiple critical paths.

What methods are used to calculate the Critical Path?

The methods used to calculate the critical path are the Project Evaluation and Review Technique (PERT) and the Critical Path Method (CPM).

The PERT and CPM methods began to be developed in the 1950s to assist managers in scheduling, monitoring and controlling large, complex projects. The CPM method (1957) was implemented as a procedure to assist in the construction and maintenance of chemical plants. The PERT technique was developed independently in 1958 for the U.S. Navy's Polaris project.

Although both methods are similar, they used different techniques to estimate task durations. The PERT method used three different time estimates for the duration of each task, plus it calculated the probability of completing the project at a given time. The CPM method used a single duration for each task; however, it also analyzed the additional costs that would be incurred if the project is accelerated.

The differences between the two techniques are now considered to be minimal; therefore, we can refer to both as an overall method called PERT CPM .

How to calculate the critical path?

To calculate the critical path we will follow the following steps:

• Step 1: Obtain the project data. Make a list of all the activities of the project along with their dependencies and their specific times.
• Step 2: Elaborate the network diagram. We have written a post that explains how to elaborate the project network diagram step by step.
• Step 3: Calculate the Early Start and Late Start Times. Determine the Early Start and Late Start Times for each activity.
• Step 4: Calculate the Early Finish and Late Finish Times. Determine the Early Finish and Late Finish Times for each activity.
• Step 5: Calculate the slack time. The critical path must be determined by finding out the slack for each activity of the process. The activities where there is no slack are the ones making up the critical path.

How to Calculate Early Start, Late Start, Early Finish, Late Finish and Slack (Float)

To visualize the calculation of these values, we will use the following graphic representation of the activity:

Duration (t):

Indicates the time it takes to complete the activity.

Early Start Time (ES):

This is the earliest time that an activity can be started assuming all previous activities have been completed beforehand. For activities that have more than one precedent, the ES is the greatest of the late start time of their precedents.

Early finish Time (EF):

This is the earliest time that an activity can finish. It is equal to the early start time plus its estimated duration (t):

EF = ES + t

Late Finish Time (LF):

This is the latest time at which an activity can be completed without delaying the entire project. It is obtained by equaling the late start time of the activity that immediately follows. If activities have more than one task immediately following them, the LF will be the least of the late start time of those activities.

Late Start Time (LS):

It is the latest time an activity can begin without delaying the whole project. It is equal to the Late Finish Time minus the expected duration of that activity (t):

LS = LF – t

Slack – Float (S):

A period of time when an activity can be delayed without causing the entire project to be delayed. All activities contained in the critical path have zero slack.

Here is how it is calculated mathematically:

S = LS – ES = LF – EF

We will illustrate these concepts with an example:

Imagine that your professor asks you to write an essay to be submitted in 15 days.

According to the length of the topic, it will take you approximately 1 week to prepare it. If you are a very responsible person, you will probably start the essay as soon as possible. The earliest start time (ES=0) , represents the first moment when you can start your essay:

If you start your project at point 0; you will have it ready at point 7. That final value represents the early finish time (EF=7) .

Now let's suppose that you like to do your activities at the last minute; most likely you want to finish your essay right on the day of the presentation. That day would be point 15 and represents the late finish time (LF=15) . You cannot exceed that point because you will no longer submit the paper on time.

In order for you to finish your paper on the 15th day, you have to start 7 days earlier (the time it takes to do the rehearsal); therefore you must start on the 8th day. This point represents the late start time (LS=8) . If you start after this date you will not be able to submit your work on time.

The 8 free days you have between the time you start work and the date of submission is the slack (float) in your activity.

Slack = LS – ES = LF – EF

Slack = 8 – 0 = 15 – 7 = 8

If we change the scenario and our teacher gives us only the one-week deadline to submit the essay. We will no longer have any free time (slack) so I must start working on the essay from the very beginning to get it done on time. Since this activity has no chance of being delayed, we call it a critical activity .

In project management, it is required to calculate these values for each activity which is achieved through a two-path process: a forward path to calculate ES and EF; and a backward path to calculate LS, LF and slack (float).

This procedure will be detailed by means of solved examples:

Draw the activity-on-node (AON) project network associated with the following activities for Dave Carhart’s consulting company project.

• How long should it take Dave and his team to complete this project?
• What are the critical path activities?

Solution 1:

The network diagram would look as follows:

The development of this diagram was explained in detail in our article on creating PERT CPM diagrams . The number at each node represents the duration of each activity.

Forward path

We will now perform the forward path to calculate the ES and EF with an analysis of each activity.

Start node:

This dummy node has all values equal to zero.

Activity A:

Since it is the first activity, its ES will be equal to the EF of the starting node (zero); the EF is calculated as follows:

EF = ES + activity time

EF A = 0 + 3 = 3

Activity B:

It has as precedent only activity A; therefore its ES will be equal to the EF of activity A. In the same way as the previous node, the EF of activity B is calculated by adding its ES + the corresponding time:

EF B = 3 + 4 = 7

Activity C:

It has as precedent only activity A; therefore its ES will be equal to the EF of activity A. The EF of activity C is calculated by adding its ES + the corresponding time:

EF C = 3 + 6 = 9

Activity D:

It has as a precedent only activity B; therefore its ES will be equal to the EF of activity B. The EF of activity D is calculated by adding its ES + the corresponding time:

EF D = 7 + 6 = 13

Activity E:

It has as a precedent only activity B; therefore its ES will be equal to the EF of activity B. The EF of activity E is calculated by adding its ES + the corresponding time:

EF E = 7 + 4 = 11

Activity F:

It has as precedent only activity C; therefore its ES will be equal to the EF of activity C. The EF of activity F is calculated by adding its ES + the corresponding time:

EF F = 9 + 4 = 13

Activity G:

It has as precedent only activity D; therefore its ES will be equal to the EF of activity D. The EF of activity G is calculated by adding its ES + the corresponding time:

EF G = 13 + 6 = 19

Activity H:

This activity has two precedents: E and F; therefore its ES will be equal to the highest EF of both activities. In this case, activity F has the highest value with 13. The EF of activity H is calculated by adding its ES + the corresponding time:

EF H = 13 + 8 = 21

The end fictitious node is joined with the last activities G and H; and the highest value of the EF of both activities is placed as ES: 21. This value represents the total duration of the project. As this node has zero duration (because it is fictitious) its EF will be equal to 21 + 0 = 21.

Backward path

To finalize the critical path calculation we will perform the backward traversal to calculate the LF and LS, starting from the final node; placing the values at the bottom of the node as follows:

For the end node the LF value is equal to the project duration (21). The LS is calculated by subtracting the LF minus the duration (zero).

LS End = 21 – 0 = 21

Since the final node is the only successor to activity H, its LF will be equal to the LS of the final node (21). The LS of activity H is calculated by subtracting its LF minus its duration:

LS H = 21 – 8 = 13

Since the end node is the only successor of activity G, its LF will be equal to the LS of the end node (21). The LS of activity G is calculated by subtracting its LF minus its duration:

LS G = 21 – 6 = 15

Since activity H is the only successor of activity F, its LF will be equal to the LS of activity H (13). The LS of activity F is calculated by subtracting its LF minus its duration:

LS F = 13 – 4 = 9

Since activity H is the only successor of activity E, its LF will be equal to the LS of activity H (13). The LS of activity E is calculated by subtracting its LF minus its duration:

LS E = 13 – 4 = 9

Since activity G is the only successor of activity D, its LF will be equal to the LS of activity G (15). The LS of activity D is calculated by subtracting its LF minus its duration:

LS D = 15 – 6 = 9

Since activity F is the only successor of activity C, its LF will be equal to the LS of activity F (9). The LS of activity C is calculated by subtracting its LF minus its duration:

LS C = 9 – 6 = 3

How activity B has as successors activities D and E, its LF will be equal to the smaller value of the LS of both. In this case, since both have a value of 9; that value will be the LF of activity B. The LS of activity B is calculated by subtracting its LF minus its duration:

LS B = 9 – 4 = 5

How activity A has as successors activities B and C, its LF will be equal to the smaller value of the LS of both. In this case, the lowest value is that of activity C (3); therefore, that value will be the LF of activity A. The LS of activity A is calculated by subtracting its LF minus its duration:

LS A = 3 – 3 = 0

Initial Node:

Using the same analysis as above we complete the values of the initial node with zero.

Finally we calculate the slack for each node with the following formula:

The final graph would look like this:

The activities with zero float (marked in red) are the critical activities. In this example, these activities follow a single path that will be our critical path: A – C – F – H . Total project time is 21 days.

Shirley Hopkins is developing a program in leadership training for middle-level managers. Shirley has listed a number of activities that must be completed before a training program of this nature can be conducted. The activities, immediate predecessors, and times appear in the accompanying table.

Provide the following:

• AON diagram for these precedencies
• What is the critical path?
• What is the total project completion date?
• What is the slack time for each individual activity?

Solution 2:

We will solve this example by showing the results and analysis of our critical path method calculator :

Each activity is broken down by its precedents and descendants:

This table serves as a guide to build our  network diagram . Two dummy activities were added to show the start and end. The activities with  0 (zero) slack  are the ones that make up the  critical path .

CPM Network Diagram

CPM Network Diagram with Calculations of ES, EF, LS, LF and Float

The following table presents the results to determine the critical path:

• Early Start (ES):  It is equal to the Early Finish to the activity's precedent. If it has more than one precedent, the highest value is taken.
• Early Finish (EF):  It is equal to the Early Start of the activity plus its duration (t). EF = ES + t.
• Late Start (LS):  It is equal to the Late Finish minus its duration (t). LS = LF – t.
• Late Finish (LF):  It is equal to the late start of the activity that follows. If it has more than one successor, the lowest value is taken.
• Slack (S):  It can be calculated in two ways. S = LS – ES = LF – EF. Activities with zero clearance make up the critical path.

The critical path is: B → D → E → G

The total project time is: 26 hours

Final Reflection

The critical path shows us the main activities that will determine the total time of the project; that is why Project Managers must be aware of the fulfillment of each one of them. This does not mean that the other activities should be neglected; on the contrary, if they are delayed longer than their slack, the project will have problems to finish on time.

With the help of our entry, we are confident that you will gain more understanding about the CPM technique and how it can be used to calculate critical path.

Finally, we invite you to follow us on our social networks and join our Facebook group where we can exchange more information with the participants.

Introduction to PMP Certification

• PMP Exam – All You Need To Know Regarding PMP Certification
• Top 10 Reasons To Get PMP® Certified in 2024
• What is PMP®Certification? – All you need to know about PMP®
• PMP Certification – Become A Certified Project Management Professional®

PMBOK Guide 6

• PMBOK 6th Edition – 10 Knowledge Areas and 49 Processes
• PMP Exam Prep – Best Way to Prepare for PMP Certification Exam

Project Management Basics

• Project Management – Phases and Methodologies
• Project Management Life Cycle – Everything You Need to Know
• Project Management Tools – Helping Aids of Project Managers
• What is Gantt Chart in Project Management?

Knowledge Areas

• Top 10 Project Management Knowledge Areas (PMBOK)
• Project Integration Management – Know How To Integrate Processes
• Project Scope Management – Know How To Manage Project Efficiently
• Project Cost Management – Know How To Manage Your Budgets
• Project Time Management – How To Optimize Project Schedule
• Project Quality Management – How To Optimize Project Quality

What is Project Resource Management and How to Perform it?

• How To Remove Project Clutter Using Konmari?
• Project Communication Management – What Makes A Project Successful?
• Project Risk Management – Know How to Mitigate Risks
• What Is Project Procurement Management And How To Perform It?
• Learn how to Perform an Effective Project Stakeholder Management

PMP Interview Questions

• Top 50 PMP Exam Questions and Answers For 2024

Top 30+ Project Manager Interview Questions and Answers in 2024

Career guidance.

• Project Manager Salary: How Much Does A Project Manager Earn?

How to Build an Impressive Project Manager Resume?

• What are the Project Manager Roles and Responsibilities?
• PMP vs PRINCE2 – Which Certification to Choose?

Project Management and Methodologies

What is critical path method (cpm) in project management.

The critical path method (CPM) is a prominently utilized project management method for timely project work within budget and time-based limitations. Before diving into CPM’s significance in project management, let us first decode exactly what a critical path method is.

What is Critical Path Method?

Notably, the critical path method is a project management methodology that describes a strategy for successfully identifying activities required to finish a project. It primarily works as a project management approach to help schedule and track different aspects of a project to ensure optimum results.

What is Critical Path in Project Management?

CPM is a widely leveraged methodology by project managers to plan a project pipeline from start to end. This method breaks different stages of a project into separate work tasks, creates a flow chart out of these stages and then aligns the timeline for them based on each task’s significance.

Why Use the Critical Path Method in Project Management?

Though it may look risky to use a critical path in project management, it does have some advantages. And, these are:

• It improves efficiency and resource allocation. Since project managers identify the most critical tasks, they can prioritise those and allocate resources effectively.
• It reduces the risk of delays by painting out potential bottlenecks.
• It helps in creating realistic project schedules, as project managers consider various task dependencies and avoid being overly optimistic about schedules.
• It promotes better communication and collaboration in the team. Usually, a lot of visual diagrams are used in CPM, which are great for a clear understanding of the project.
• It encourages informed decision-making, as there is very little room for mistakes.
• Data gathered through critical path analysis in project management is later used to benchmark future projects.

If you are curious about how project managers handle all this and more, then you can sign up for Edureka’s PMP certification and get live training on such project management methods and more.

But, if you are a complete beginner and hoping to kickstart your journey right from scratch, then check out the project management tutorial to set the base.

How to Find the Critical Path in Project Management?

Now that you have explored so much about CPM in project management, let’s examine how to calculate the critical path.

1. List activities

This is the cornerstone of CPM, where you list and identify each individual job needed to finish your project. The most widely used strategy for this step is the work breakdown structure (WBS). It breaks the project down into smaller, more manageable jobs to ensure that you cover everything in this step, beginning to end.

2. Identify dependencies

Once you have tasks at hand, you need to establish a correlation and find dependencies between them. Dependencies mean a relationship where one task needs to be completed (or at least partially completed) before another can begin. Dependencies can be mandatory or discretionary.

3. Create a network diagram

CPM heavily relies on visual representations of project schedules. These diagrams clearly show the tasks and their dependencies so the team is well aware of their responsibilities. Common network diagram tools include the arrow diagramming method (ADM) and the precedence diagramming method (PDM).

4. Estimate task duration

A project manager needs to assign a realistic time estimate to each task on the list. While making these estimates, he/she considers factors like resource availability, task complexity, and potential risks.

5. Calculate the critical path

This is the heart of CPM. You can use the forward pass method to calculate the critical path.

To do this, you have to start at the project’s beginning and calculate the “earliest start (ES)” and “earliest finish (EF)” times for each task. ES is the earliest possible time a task can start, considering its dependencies. EF is the earliest time a task can be completed based on its ES and duration.

At the end of making the critical path, your calculation should show EF = ES + duration.

Remember that the starting activity always has an ES time of 0.

6. Calculate the float

In CPM, float refers to the leeway or buffer period a task has before it starts impacting the overall project. There are two types of float.

1. Total Float (TF):

This is the total amount of time an activity can be delayed without affecting the project completion date.

There are two ways to calculate this:

• TF = LS – ES (latest start – earliest start)
• TF = LF – EF (latest finish – earliest finish)

2. Free Float (FF):

It is the amount of flexibility an activity has within the context of its immediate dependencies.

You can use this formula to calculate FF.

• FF = ES (next task) – EF (current task)
• Positive float means the activity has some flexibility and can be delayed by that amount without impacting the project schedule.
• Zero float means the activity is on the critical path. Any delay in this activity will directly delay the project’s completion.
• Negative float means the activity has already started later than its latest allowable start time and is currently delaying the project schedule.

The steps may sound very simple theoretically, but the execution part is a bit tricky. You will need to use multiple project management to ols to eliminate as many human errors as possible.

How to Use Critical Path in Project Management?

After we understand what is critical path in project management and how it is calculated, we can discuss how to use it.

➢  Compress schedules

You can use CPM to identify ways to shorten your project timeline. It is done with the help of two methods: fast-tracking and crashing.

In fast-tracking, you identify the tasks that can be done simultaneously and get them done.

While crashing, you allocate more resources to a specific task to speed it up.

➢  Resolve resource shortages

CPM also helps in identifying resource constraints. Based on the analysis, you can then move team members, negotiate for budget/time or reschedule tasks.

➢  Compile data for future use

Data gathered through CPM can be used as guidelines for future projects, allowing for more precise calculations. Some of the most crucial data points include task durations, dependency mappings, and the evolution of the critical path throughout the project.

By and large, CPM is a great tool that is not limited to project timeline creation. It supports project managers in their ongoing efforts to sharpen their decision-making abilities and get ready for difficult circumstances.

If you wish to discover more about project management practices, then check out Edureka’s project management courses to redeem that competitive edge needed to thrive in this domain.

Frequently Asked Questions

1.   is pert or cpm better.

Both methods are good for different purposes. PERT is good for projects without setting due dates, while CPM is better for projects with strict deadlines.

2.   How is the critical path calculated?

You can calculate the critical path by simply identifying the shortest route on the diagram or by using the formula: earliest finish (EF) = earliest start (ES) + duration. Here, ES will always be 0.

3.   What is the purpose of the critical path?

CPM helps project managers identify the longest stretch of dependent tasks of a project and what can be the shortest time to finish the project.

4.   What is a critical path example?

A very relatable example of a critical path is planning a wedding. The ultimate goal is executing the wedding ceremony, but smaller tasks like picking outfits, booking the venue, inviting guests, etc., need to be completed. So, for example, “choose wedding date” would depend on “book reception venue.”

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