Download Mobile App1Estimation Inputs
Weights the most likely estimate 4x. Industry standard for PERT.
2Expected Time (tE)
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time units (days/hours)
Formula: tE = (O + 4M + P) ÷ 6
3Risk Metrics
σ (Std Dev)
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σ² (Variance)
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Formula: σ = (P − O) ÷ 6
Quick Formula Reference
Beta Distribution (PERT)
tE = (O + 4M + P) ÷ 6Most accurate for project estimation. Weights the most likely estimate 4x.
Triangular Distribution
tE = (O + M + P) ÷ 3Simpler calculation. Use when estimates have equal weight.
Standard Deviation
σ = (P - O) ÷ 6Measures estimation uncertainty
Variance
σ² = [(P - O) ÷ 6]²Sum for critical path variance
Understanding PERT Estimation
The Program Evaluation Review Technique (PERT) is a statistical tool used to analyze the time required to complete project tasks. It accounts for uncertainty by using three estimates instead of one.
When to Use PERT
- New projects with high uncertainty
- Complex tasks with variable durations
- When historical data is limited
- For critical path analysis
Key Benefits
- Accounts for uncertainty in estimates
- Provides approximate schedule ranges for comparison
- Helps identify schedule risks early