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Difference between PERT and CPM

Project management can be understood as a systematic way of planning, programming, execution, monitoring, control of the different aspects of the project, in order to reach the goal reached at the time of the project formulation. PERT and CPM are the two network-based project management techniques, which show the flow and sequence of activities and events. The (Project) Management and Review Technique (PERT) program appropriate for projects where I don't know how long it takes to complete several tasks.

On the other hand, the critical path method or CPM suitable for projects that are recurring in nature.

The two scheduling methods use a common approach for network design and for ascertaining its critical path. They are used in the successful completion of a project and therefore used in combination with each other. However, the truth is that CPM differs from PERT in a way in which the latter focuses on time while the former places an emphasis on the cost-time trade-off. Likewise, there are many differences between PERT and CPM, which we will discuss in this article.

Comparative chart

Basis for the PERCCPM comparison
Sense PERT is a project management technique, used to manage the uncertain activities of a project. CPM is a statistical project management technique that manages well-defined project activities.
What is it? A time planning and control technique. A method to control costs and times.
Orientation Event-oriented Activity-oriented
Evolution Evolved as a research and development project Evolved as a construction project
Template Probabilistic model Deterministic model
It focuses on Time Exchange of costs in terms of time
The estimates Three estimates An estimate of the time
Appropriate for High precision time estimation Reasonable time estimate
Management of Unpredictable activities Predictable activities
Nature of the works Non-repetitive nature Repetitive nature
Critical and non-critical activities No differentiation differentiated
Useful to Research and development project Non-research projects such as civil construction, shipbuilding, etc.
Crash concept Not applicable Applicable

Definition of PERT

PERT stands for Program (Project) Evaluation and Review Technique, where planning, programming, organization, coordination and control of uncertain activities take place. The technique studies and represents the tasks undertaken to complete a project, to identify the minimum time for completing a task and the minimum time needed to complete the whole project. was developed in the late 1950s. It aims to reduce the time and costs of the project.

PERT uses time as a variable representing the planned resource application along with performance specifications. In this technique, first of all, the project divided into activities and events. After the correct sequence has been ascertained, a network is created. After the time required for each activity has been calculated, the critical path (the longest path connecting all events) is determined.

Definition of CPM

Developed in the late 1950s, Critical Path Method or CPM an algorithm used to plan, plan, coordinate and control the activities in a project. Here, it is assumed that the duration of the activity is fixed and certain. CPM is used to calculate the most recent and most recent start time for each activity.

The process differentiates between critical and non-critical activities to reduce time and avoid queue generation in the process. The reason for identifying critical activities which, if an activity is delayed, will cause the whole process to suffer. This is why it is called as a critical path method.

In this method, first, a list is prepared including all the activities necessary to complete a project, followed by the calculation of the time required to complete each activity. Next, the dependency between the activities is determined. Here, 'path' defined as a sequence of activities in a network. The critical path is the path with the highest length.

Key differences between PERT and CPM

The following are the most important differences between PERT and CPM:

  1. PERT is a project management technique, in which uncertain activities are planned, programmed, organized, coordinated and controlled. CPM is a statistical project management technique in which planning, programming, organization, coordination and control of well-defined activities take place.
  2. PERT a time planning and control technique. Unlike CPM, what a method to control costs and times.
  3. While PERT evolved as a research and development project, CPM evolved as a construction project.
  4. PERT set based on events while CPM aligned to activities.
  5. A deterministic model is used in CPM. Conversely, PERT uses a probabilistic model.
  6. There are three times the estimates in PERT, i.e. the optimistic time (a), the most probable time, the pessimistic time (tp). On the other hand, there is only one estimate in CPM.
  7. The PERT technique is best suited for a highly accurate time estimate, while the appropriate CPM for a reasonable time estimate.
  8. PERT deals with unpredictable activities, but the CPM deals with foreseeable activities.
  9. PERT is used when the nature of non-repetitive work. On the contrary, CPM implies work of a repetitive nature.
  10. There is a demarcation between critical and non-critical activities in CPM, which is not the case with PERT.
  11. PERT the best for research and development projects, but CPM for non-research projects such as construction projects.
  12. Stopping a compression technique applied to CPM, to shorten the duration of the project and the lowest additional cost. The crash concept is not applicable to PERT.

Video: PERT Vs CPM


The difference between these two project management tools becomes confused as the techniques merge with the passage of time. That's why, in most projects, they are used as a single project. The main point that distinguishes PERT from the CPM is that the former gives the extreme importance of time, that is, if time is reduced to a minimum, consequently also the cost will be reduced. However, cost optimization the basic element, in the second.