What is PERT in Project Management? - Top Features and Time Estimates

PERT is the Program Evaluation and Review Technique, which is a tool used to efficiently manage a particular project by the determination of the realistic time required to finish a particular project. The task in a project is represented by PERT charts that help to easily plan, schedule and coordinate the project team members who are involved in the work.


Important Features of PERT

The important feature of PERT a project manager must know are:

  1. PERT is a combination of simple statistical methods. It in its cores is all about management probabilities.
  2. PERT and CPM have some similar characteristics, but their focus are different.
  3. PERT similar to other networking techniques, breaks down the tasks to detailed activities.
  4. After obtaining the activities, a Gantt Chart is created that illustrates the interdependencies of the activities.
  5. In the Chart, each node represents each even connected by arrows. The activities are represented by arrows.
  6. Next, the time estimates are determined- Earliest Time, latest Time and also slack for each activity.
  7. The PERT hence is an event-oriented project technique
  8. It is the best technique for newly developed projects than repetitive projects.

Time Estimates Used in PERT

The three estimation times used in PERT are:
  1. Optimistic Time Estimate (To)
  2. Most Likely Time (Tm)
  3. Pessimistic Time (Tp)
The three-time estimates are determined for each activity. 

Optimistic Time Estimate(To) in PERT

It is the fastest time an activity can be completed. Here the assumption made is that all the resources are available and all the predecessor activities are completed as per the plan.

Most Likely Time(Tm) in PERT

If the project managers are demanded only to submit a single time for each activity, then they submit the most likely time.

Pessimistic Time(Tp)

This is the maximum time required to finish an activity. For cases when everything goes wrong and gets delayed, this time estimate is considered.

Expected Completion Time (T)  and Possible Variance (V) in PERT




T = (To + 4Tm + Tp )/6

Standard Deviation = (Tp - To)/6

Variance V =  Sqaure of Standar Variation = (Tp-To)2/36


Read More: PERT- Pros and Cons





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