Active Formula
Program Evaluation & Review Technique
PERT · Weighted Average
E = (O + 4M + P) ÷ 6
Weights the most likely estimate 4× more than optimistic or pessimistic. Produces a beta-distribution mean — the industry standard for schedule and cost estimation when variability matters.
Enter Estimates
Unit
d
Best case
d
Realistic case
d
Worst case
Result
—
PERT
Expected Duration
—
days
Optimistic
—
Most Likely
—
Pessimistic
—
Standard Deviation (σ)
(P − O) ÷ 6 — measures estimate spread
—
Estimate Range
—
Estimate
—
Confidence Intervals
68% Confidence
—
±1σ
95% Confidence
—
±2σ
99.7% Confidence
—
±3σ
Interpretation
—
Task Summary
Total: — days
Project Total Estimate
—
Method Reference
PERT
E = (O + 4M + P) ÷ 6
Weighted average. Most Likely gets 4× weight. Best for risk-aware schedules and PMI-aligned estimates.
Triangular
E = (O + M + P) ÷ 3
Simple average. Equal weight to all three. Use when data is scarce or for quick early-phase estimates.