PERT Three Point Estimation

Use PERT three point estimation to calculate realistic task durations by accounting for optimistic, pessimistic, and expected scenarios.

5 time blocks, 35 minutes in total.

Time blocks

Define Task Scope and Deliverables: 5 min
Clarify task boundaries and list specific completion criteria
Determine Optimistic Duration: 5 min
Estimate best case duration if zero blockers or delays occur
Determine Most Likely Duration: 10 min
Estimate typical duration under standard working conditions
Determine Pessimistic Duration: 10 min
Estimate worst case duration if multiple setbacks occur
Compute PERT Expected Duration: 5 min
Calculate weighted expected time using the classic PERT formula

About this routine

PERT three point estimation was developed by the United States Navy in 1957 to improve project management accuracy. Instead of relying on a single guess, this method collects three distinct estimates for any given task: optimistic, most likely, and pessimistic.

By weighting the most likely outcome four times more heavily than the extremes, the formula reduces single value bias and accounts for variance. Project managers and software engineers use this structure to set defensible timelines and identify high risk work blocks before execution begins.

This 35 minute session guides you through breaking down a task, scoring all three time estimates, and computing the final weighted average alongside standard deviation.

Why this routine works

Reduces optimistic bias in project planning
Accounts for unexpected delay risks using a structured formula
Produces mathematically defensible task estimates
Improves schedule accuracy across uncertain engineering or creative projects

FAQ

What is PERT three point estimation?

It is a project management method that calculates task duration using optimistic, most likely, and pessimistic estimates.

What is the formula for PERT estimation?

The PERT formula adds the optimistic estimate, four times the most likely estimate, and the pessimistic estimate, then divides the sum by six.

How does PERT estimation differ from Planning Poker?

Planning Poker relies on team consensus scoring with relative story points, while PERT uses individual scenario durations weighted mathematically.

Sources

Project Management Institute, PMBOK Guide
United States Navy Special Projects Office, PERT Summary Report (1958)