Charlotte Davis

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Critical Path Method for Project Management

Critical path method chart, diagram. Determine critical path.
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The critical path method (CPM) is a project management technique that can be used for projects of all kinds imaginable. From the most significant organizational restructuring projects in the workplace to making sure the Thanksgiving feast comes out exactly on time.

Developed in the 1950s by a chemical company developing a kind of synthetic rubber, the critical path method has become an extremely popular management method due to its effectiveness in organizing the work in a way that allows reaching the expected goals in established time frames.

It is largely based on the Program Evaluation Review Technique (PERT), which was used successfully to complete the engineering and development of the US Navy’s submarine-based Polaris missile in a time period estimated to be two years shorter than it otherwise would have been. The foundation of the technique is focusing attention on activities that affect the total project duration.

PERT also highlights unpredictable issues or delays – by creating three possible outcome timelines, the most optimistic, most pessimistic, and most realistic, project managers will be ready for all eventual outcomes (in theory!).

But there are some significant differences between PERT and CPM, one of the main ones being the fact that PERT uses the probabilistic model for scheduling tasks and predicting the duration of the project, while CPM relies on a deterministic model to achieve the same outcome.

What is critical path in project management? What are the main components of the Critical Path Method? You’ll find all the answers in this article.

What Is the Critical Path Method in Project Management?

The Critical Path Method is the process of identifying the sequence of tasks that take the longest time to complete. Such a sequence is called the critical path, whereas the individual tasks in the path are called the critical tasks.

With this technique, it is easy to estimate how much time you’ll need to finish the project. The duration of a critical path is the absolute minimum time needed for a project to be completed.

Why can CPM be an immense help when working on complex projects? This method allows you to:

  • Precisely calculate the duration of critical path activities.
  • Identify dependencies between tasks and all potential project scheduling challenges.
  • Prioritize tasks taking into account their float or slack time, which helps with the proper resources distribution and scheduling.
  • Identify critical tasks with no slack time and ensure they are finished on time.
  • Monitor your project progress.
  • Benefit from various schedule compression techniques, for example, fast-tracking.

How To Calculate Critical Path of an Entire Project?

To calculate the project’s critical path, project managers must first create a network diagram of the project. This should include all of the tasks and activities that must be completed in order for the project to be successful. The dependencies between tasks should also be represented by arrows in the network diagram.

Once the network diagram has been created, project managers can use the critical path algorithm to calculate the critical path. This is done by calculating the earliest possible start and finish dates for each task in the network and then using this information to calculate the total duration of the project.

It is important to note that the critical path may change over time as tasks are completed, or new tasks are added. For this reason, it’s crucial to continually monitor the critical path to ensure that the project is on track.

Key Elements of the Critical Path Method Step by Step

The Critical Path Method has several key elements, which could be broken down into a few steps.

  1. Identify tasks – Identify high-level tasks to be completed in the project first, followed by non-critical tasks.
  2. Identify task dependencies – Line up the tasks in order of dependency to construct a clear work breakdown structure.
  3. Create the Network Diagram – Present your line-up in a visual way by creating a critical path diagram. You can use a PERT or Gantt chart for this purpose.
  4. Set your time frames – Estimate each task completion times. Set the beginning and end date for each task. Remember to consider dependent tasks and their order while planning your project schedule.
  5. Perform Resource Leveling – Resource leveling is all about adjusting the start and finish dates of your tasks based on the resources you have at your disposal.
  6. Determine the critical path for your project – Find the longest sequence of tasks in your project chart. This will be your critical path!
  7. Update as needed – The last step is about resource planning and task management as you go. Adapt to changes in your project schedule to meet your project’s deadline.
Flat vector illustration for Critical Path Method

Explaining Float/Slack

Float/slack is an important concept in the Critical Path Method. It refers to the amount of times that a task can be delayed without impacting the project’s overall timeline. Tasks that have float/slack are said to be “floating” or “slack” tasks, while tasks that must be completed on time are said to be “critical” tasks.

Float/slack can be calculated by subtracting the duration of the task from the earliest start date for the task. For example, if the earliest start date for a task is 10 days and the duration of the task is 5 days, the float/slack for the task is 5 days.

Float/slack is important because it allows project managers to identify project tasks that can be delayed without impacting the overall timeline. This can be useful for managing unexpected delays or risks, as well as identifying areas where time can be saved.

Early Start and Early Finish

Every task in your project has its early start and early finish time. It’s the earliest possible time a task can start and finish. You can calculate early start date and finish date by recording the time it took to complete a similar task (for example, using time-tracking software) and applying this information to your current project tasks.

Then you must add the ES and EF times to get each task’s early start and early finish date. This technique, called a Forward Pass, can help you shape your critical path process and better estimate the project completion date.

Late Start and Late Finish

It’s also important to calculate the late start and late finish times for your subsequent tasks. These are the latest dates on which the tasks can start and finish without it affecting the project’s completion date.

A project manager can calculate the late start date by going through the project’s critical path and subtracting the time each task will take to complete. This is a Backward Pass, and it is helpful to determine the latest time at which tasks can start and finish.

Common Pitfalls of the Critical Path Method

As with any project management tool, there are certain drawbacks that you should be aware of when using the Critical Path Method. The most common pitfalls include not taking into account the dependencies between tasks, overlooking potential risks, and not monitoring the critical path on a regular basis.

When using the CPM, it is important to consider the dependencies between tasks. If a task is taking longer than expected, it may affect the completion date of other tasks in the network. This could have a significant impact on the whole project timeline and should be carefully monitored.

Additionally, you should be aware of potential risks and plan for how to respond to them. For example, if a task is taking longer than expected, project managers should consider alternative approaches or ways to streamline the task. Like with everything else in life, it’s beneficial to be responsive to deviations from the original plan and prepare Plan B ahead of time.

It’s also imperative to monitor the critical path on a regular basis. As tasks are completed, or new tasks are added, the critical path may change, so it’s really an ongoing process.

Differences Between the Critical Path Method Chart and Gantt Chart

A critical path analysis chart and a Gantt chart are both project management tools that aim to maximize time and cost efficiency when it comes to getting the job done. Here are the main differences:

CPM helps managers demonstrate and understand critical and non-critical paths and accurately calculate project duration.

Gantt charts also help to calculate total project duration but do not focus on how critical each task is, but rather the order of all the tasks in the diagram.

Critical path method charts are presented in a network diagram form, with linked cells, whereas a Gantt chart consists of horizontal bars in a bar chart formation.

Gantt Charts are timeline-based diagrams that show the tasks and activities of the project in relation to time, which is one of the main differentiating factors between this method and Critical Path analysis.

Gantt Charts can be a valuable help with identifying the critical path of your project and understanding the dependencies between all the project activities.

Gantt Progress Line

Tools and Software for Implementing the Critical Path Method

There are a variety of tools and software available for implementing the Critical Path Method. These tools and software can help project managers create network diagrams and calculate the critical path.

Microsoft Project is a popular project management software that includes CPM functionality. It allows project managers to create network diagrams and calculate the critical path. Additionally, it can be used to track project progress and identify potential risks.

There are also a variety of online tools and software specifically designed for project management. You can find lots of valuable resources on the best project management software on Productively Blog, so you don’t have to do your own tedious research — save time and learn about the best tools for streamlining your work processes and improving tasks management!


The Critical Path Method (CPM) is an important tool for project managers. It helps identify the tasks and activities that must be completed in order for the project to be successful, understand the dependencies between tasks, and adjust project schedules accordingly.

CPM is a powerful tool that can be used in a variety of projects, including, but not limited to, the construction of buildings, the development of software, or movie productions.

If you are looking for a powerful tool to help you manage your projects, the Critical Path Method is an excellent strategy to improve your project planning and organize your work in a way that makes the most sense and will offer you the best chance of succeeding in the established time frames.

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