Key Differences Between PERT and CPM

Excellent project management abilities are critical to the success of any business. These abilities are critical in determining the budget and time required to meet a project’s objectives. PERT and CPM are two typical statistical methodologies used to ensure project completion in a timely and cost-effective manner.

Despite the fact that both strategies result in the design of the project’s network, they are not the same.

PERT and CPM vary primarily in that PERT refers for Program Evaluation and Review Technique while CPM stands for Critical Path Method. PERT handles unpredictability, whereas CPM manages predictability. PERT is concerned with events, whereas CPM is concerned with activities.

The primary objective of PERT is to plan and manage time, whereas the primary focus of CPM is to control cost and time.

PERT and CPM

What is PERT?

PERT stands for Program (Project) Evaluation and Review Technique, and it refers to the process of planning, scheduling, organizing, coordinating, and regulating unpredictable operations. The technique investigates and represents the tasks undertaken to finish a project in order to determine the shortest time required to complete a task and the shortest time required to complete the entire project. It first appeared in the late 1950s. Its goal is to shorten the project’s duration and expense.

PERT makes use of time as a variable to indicate the planned resource application as well as performance specifications. First and foremost, the project is separated into activities and events using this technique. After determining the right sequence, a network is built. The time required for each action is then calculated, and the critical path (the longest path connecting all of the events) is identified.

What is CPM?

Critical Path Method, or CPM, is an algorithm developed in the late 1950s that is used for project planning, scheduling, coordination, and management. It is assumed that the length of the activity is set and predictable. CPM is used to determine the earliest and latest start times for each activity.

The procedure distinguishes between important and non-critical actions in order to save time and avoid queue generation. The reason for identifying key tasks is because if any action is delayed, the entire process suffers. This is why it is known as the Critical Path Method.

In this procedure, a list of all the actions required to accomplish a project is created first, followed by a calculation of the time required to perform each activity. The dependency between the activities is then determined. A ‘path’ in this context is defined as a succession of activities in a network. The essential path is the one that is the longest.

Similarities

PERT and CPM have very similar approaches. Their applications are comparable.

There are only two differences between them.

  • In CPM, each activity has only a single estimation. A single activity in PERT may have three time estimates.
  • CPM allows for the estimation of time and cost, as well as the control of time and cost. PERT is a planning tool that only provides for time control.

Key Differences

The following are the key differences between PERT and CPM:

  • PERT is a project management technique that involves the planning, scheduling, organizing, coordinating, and controlling of unpredictable tasks. CPM is a statistical project management technique that involves the planning, scheduling, organizing, coordinating, and control of well-defined tasks.
  • PERT is a time management and planning technique. Unlike CPM, which is a cost and time management strategy.
  • CPM evolved as a building project, whereas PERT evolved as a research and development initiative.
  • PERT is based on events, whereas CPM is based on activities.
  • CPM employs a deterministic model. PERT, on the other hand, employs a probabilistic model.
  • In PERT, there are three time estimates: optimistic time (to), most likely time TM, and pessimistic time (tp). In CPM, on the other hand, there is just one estimate.
  • PERT is better suited for high accuracy time estimates, whereas CPM is best suited for reasonable time estimates.
  • PERT deals with unpredictability, whereas CPM deals with predictability.
  • PERT is used when the job is not repetitive in nature. CPM, on the other hand, includes repetitive tasks.
  • In CPM, there is a distinction between critical and non-critical activities that does not exist in PERT.
  • PERT is appropriate for research and development projects, whereas CPM is best for non-research tasks such as building.
  • Crashing is a compression technique used in CPM to minimize project duration while incurring the least incremental cost. The concept of crashing does not apply to PERT.

Comparison Table

Parameter of ComparisonPERT Technique CPM Technique
OrientationEvent-orientedActivity-oriented
Type of ModelProbabilistic model characterized by uncertainty in the duration of project completion.Deterministic model characterized by certainty in the duration of project completion.
Focus onFocus on the time of completion of a project.Focus on the time-cost trade-off in a project.
The Crashing ConceptThe crashing concept is not applicable.The crashing concept is applicable.
AppropriatenessSuitable for high precision time estimation of unexpected projects with non-repetitive activities.Suitable for projects with known outcomes and recurring activities. Time estimates are made in realistic forms for such initiatives.

Conclusion

The differences between the two project management tools is becoming increasingly blurred as the methodologies mix over time. As a result, in most projects, they are employed as a single project. The fundamental difference between PERT and CPM is that the former places a premium on time, implying that if time is saved, costs would be saved as well. However, with the latter, cost optimization is the most important factor.