PMP Example of Pert vs CPM Chart

The PERT formula is based on the concept of the Critical Path Method (CPM), which is a technique used to identify the order of activities in a project. Knowing what method is better would really depend on the project at hand.

If you need a more precise estimation of project duration, then PERT is the way to go. If you just need a quick estimation then go for an estimated Critical Path

PERT Formula Project Management

The PERT formula is a project management tool that is used to calculate the time necessary to complete a project. 

This formula is used to create a PERT chart, which is a graphical representation of the project timeline. 

PERT charts are used extensively in project planning and management, as they allow for a clear visual representation of the relationships between tasks

In order to use the PERT formula, you will need to know the duration of each activity in the project; it is here then used to calculate the expected duration of the project.

Benefits of PERT

By using the PERT formula, project managers can develop a more accurate picture of a project’s timeline and budget by specifying the time required to complete an activity is no easy task. 

This formula is useful because it takes into account the three different estimated times for a project (optimistic, most likely, and pessimistic) and provides a more accurate average. This can be helpful when planning and budgeting for a project.

pert formula

Example of PERT Formula in Project Management

So how does the PERT formula work? Let’s take a look at an example. 

Say you are planning a party and you need to buy some supplies. You estimate that it will take you 3 hours to buy the supplies, but you want to account for any unforeseen delays. Using the PERT formula, you would first come up with an optimistic estimate (2 hours), a pessimistic estimate (4 hours), and a most likely estimate (3 hours). 

Considering the formula above, it can be represented in this way

pert example

Therefore 3 hours is the estimated amount of time your supplies for your party will be delivered using the average of the pert formula

CPM Formula Explained in Project Management

The Critical Path method is a popular project management technique used to schedule and organize complex projects. 

The method is based on the concept of the longest path through a network of activities. This path is referred to as the Critical Path, and it represents the minimum amount of time needed to complete the project.

A critical path has the following attributes:

  • It has no slack or float time.
  • It consists of dependencies between tasks.
  • It links together all the tasks in the project.

Benefits of CPM

In project management, the Critical Path Method (CPM) is a tool used to determine the sequence of project activities and the duration of each activity. It is also a method used to identify the activities that are most likely to delay the project.

You can also use it to identify potential problems and bottlenecks. 

By understanding the critical path, you can manage your project more effectively and increase your chances of success.

Example of CPM

In order to create a critical path, you need to identify the dependencies between tasks and then order the tasks based on those dependencies. You also need to determine which tasks are float tasks and which are critical tasks.

In the below example, there are four tasks: A, B, C, and D. The green tasks represent the dependencies between the tasks. And the yellow ones are the float tasks. 

  • The critical path is the sequence A-B-C-D.

Task A cannot start until task B is complete, as task B must first be finished before task C can start and task D must start when C finishes. This is an example of how this dependency works.

Tasks E, F, and G can be performed earlier or later in the whole schedule without actually affecting the total duration of the project.

critical path example


Both of these methods can be useful in different situations, but there are also some key differences between pert and cpm are:

  • The PERT formula is a statistical approach that uses the mean, mode, and standard deviation of estimates to come up with a final estimate. It is best used when there is a lot of data available on similar tasks.
  • The Critical Path Method, on the other hand, is a deterministic approach that uses the longest path of activities to estimate the completion time. It is best used when there are less data available or when the task is very complex.
  • PERT, or the Program Evaluation Review Technique, is a more precise method that takes into account the varying durations of different tasks. PERT is typically used for larger projects with more complex task dependencies.
  • CPM, or the Critical Path Method, is a more simplified method that focuses on the minimum amount of time needed to complete a project. CPM is typically used for smaller projects with more straightforward task dependencies.

What is PERT Formula?

The PERT formula (Program Evaluation Review Technique) is a network diagramming tool used to estimate task durations. The PERT formula takes into account the optimist, pessimist, and most likely scenarios to come up with an average estimate. While it is not always 100% accurate, the PERT formula is a useful tool for project managers to have in their toolkits.

What is the Critical Path Method?

The Critical Path Method is a network-based algorithm that calculates the shortest possible duration for a project. It is based on the principle that activities must be completed in a sequence and that some activities are dependent on others. 

What are the main differences between CPM and PERT?

CPM involves breaking down a project into smaller tasks, then creating a schedule that shows which tasks need to be completed in what order it’s often used in construction projects, as it is helpful for visualizing the construction process. While the PERT is more focused on analyzing the time needed to complete each task, it is often used in large-scale projects where there are many different tasks that need to be completed.

Scroll to Top