PERT Calculator
Calculate project completion times using Program Evaluation and Review Technique
Calculate PERT Estimates
Everything goes perfectly
Normal conditions with some delays
Everything goes wrong
For probability analysis (leave empty to skip)
PERT Analysis Results
Formula: PERT = (O + 4M + P) / 6
Standard Deviation: SD = (P - O) / 6
Analysis Insights
Example: Building a Fence
Project Scenario
Project: Build a fence around property
Optimistic (O): 5 days (perfect weather)
Most Probable (M): 7 days (some weather delays)
Pessimistic (P): 9 days (worst weather)
PERT Calculation
PERT = (5 + 4×7 + 9) / 6
PERT = (5 + 28 + 9) / 6 = 42 / 6 = 7 days
SD = (9 - 5) / 6 = 4 / 6 = 0.67 days
PERT Time Estimates
Optimistic
Best-case scenario where everything goes perfectly
Most Probable
Most likely scenario with normal conditions
Pessimistic
Worst-case scenario with maximum delays
PERT Benefits
More accurate time estimates
Accounts for uncertainty
Better project planning
Risk assessment capability
Statistical foundation
Industry standard method
Understanding PERT (Program Evaluation and Review Technique)
What is PERT?
PERT (Program Evaluation and Review Technique) is a project management tool used to estimate task durations and project completion times. It was originally developed by the U.S. Navy for the Polaris missile program in the 1950s.
How PERT Works
- •Uses three time estimates to calculate expected duration
- •Weighted average gives more importance to most likely estimate
- •Provides statistical measures of uncertainty
- •Enables probability analysis for deadlines
PERT Formulas
Expected Time:
E = (O + 4M + P) / 6
Standard Deviation:
σ = (P - O) / 6
Z-Score:
Z = (D - E) / σ
When to Use PERT
- Complex projects: With high uncertainty
- New activities: Limited historical data
- Critical deadlines: Need probability analysis
- Risk assessment: Understanding variability
Note: PERT assumes a beta distribution for activity durations and is most effective when time estimates are made by experienced professionals.
PERT vs Other Estimation Methods
PERT
- • Three-point estimates
- • Statistical foundation
- • Uncertainty quantification
- • Best for uncertain projects
Single Point Estimate
- • One time estimate
- • Simple and quick
- • No uncertainty measure
- • Best for routine tasks
Historical Data
- • Past performance
- • Data-driven approach
- • Limited to similar tasks
- • Best for repeated projects