Program Evaluation and Review Technique (PERT) is a technique used to estimate project duration when there is uncertainty in activity estimates. It applies a weighted average formula to combine the optimistic, most likely, and pessimistic durations for each activity, producing a more realistic expectation of how long the activity will take.
PERT is particularly useful for projects with high variability or limited historical data.
Key Characteristics
- Three-Point Estimating – Uses optimistic (O), most likely (M), and pessimistic (P) durations
- Weighted Formula – Places more emphasis on the most likely estimate
- Focuses on Uncertainty – Designed for activities with unclear or variable durations
- Used in Network Analysis – Supports schedule modeling and critical path calculations
Example Scenarios
- A research project with experimental tasks uses PERT to account for possible delays
- Product development work with new technologies applies PERT to plan realistic timelines
- Estimating the duration of an approval process with wide variability across stakeholders
PERT Formula (Expected Duration)
Mermaid Diagram: PERT Components and Flow
flowchart TD A[Optimistic Duration-O] B[Most Likely Duration-M] C[Pessimistic Duration-P] A --> D[PERT Formula] B --> D C --> D D --> E[Expected Duration-E]
Role in Project Estimation
- Accounts for Uncertainty – Produces a more realistic activity duration
- Improves Planning Accuracy – Balances best-case and worst-case possibilities
- Supports Critical Path Method (CPM) – Enhances schedule modeling under risk
- Useful in High-Variability Work – Ideal when little reliable data is available
See also: Analogous Estimating, Bottom-Up Estimating, Parametric Estimating, Multipoint Estimating, Three-Point Estimating.