PERT Calculator
Estimate a realistic project or task duration using the PERT three-point estimation technique.
What is PERT estimation?
PERT (Program Evaluation and Review Technique) is a three-point estimation method used in project management to account for uncertainty in task durations. Instead of relying on a single guess, it combines three estimates: the optimistic time (best case), the most likely time (realistic case), and the pessimistic time (worst case).
The formula
The expected duration is calculated as a weighted average that gives four times the weight to the most likely estimate: E = (O + 4M + P) / 6. The standard deviation, which reflects how much uncertainty exists in the estimate, is calculated as SD = (P – O) / 6.
A larger gap between your optimistic and pessimistic estimates produces a higher standard deviation, meaning less confidence in the exact duration. This calculator is intended for general project planning and educational purposes, not as a guaranteed forecast.