PERT Calculator
Calculate PERT (Program Evaluation and Review Technique) estimates. Use three-point estimation (optimistic, most likely, pessimistic) to estimate project duration or cost.
How to Use This Calculator
- Enter optimistic estimate (best case scenario).
- Enter most likely estimate (typical scenario).
- Enter pessimistic estimate (worst case scenario).
- The calculator displays PERT estimate, standard deviation, and variance.
- Use this for project planning and risk analysis.
PERT Formula
PERT uses three-point estimation:
Standard Deviation = (Pessimistic - Optimistic) / 6
Variance = Standard Deviation²
Example: Optimistic 10, Most Likely 15, Pessimistic 25: Estimate = (10 + 4×15 + 25) / 6 = 15.83. Standard Deviation = (25 - 10) / 6 = 2.5. Variance = 2.5² = 6.25. The weighted average gives more weight to the most likely estimate while accounting for uncertainty.
Full Description
PERT (Program Evaluation and Review Technique) is a project management method that uses three-point estimation to estimate project duration or cost. Instead of a single estimate, PERT uses three estimates: optimistic (best case), most likely (typical), and pessimistic (worst case). This accounts for uncertainty and provides a more realistic estimate than a single point.
The PERT estimate is calculated as (Optimistic + 4×Most Likely + Pessimistic) / 6. This weighted average gives four times more weight to the most likely estimate while still accounting for best and worst cases. Standard deviation = (Pessimistic - Optimistic) / 6, which measures uncertainty. Higher standard deviation indicates more variability and risk. Variance is standard deviation squared, used in statistical analysis.
This calculator helps you create PERT estimates. Enter optimistic, most likely, and pessimistic estimates, and it calculates PERT estimate, standard deviation, and variance. Use it for project planning, task estimation, cost estimation, risk analysis, or any situation with uncertainty. PERT is especially useful when you have limited historical data or high uncertainty!
Frequently Asked Questions
What is PERT?
PERT (Program Evaluation and Review Technique) is a project management method that uses three-point estimation to estimate project duration or cost. It uses optimistic (best case), most likely, and pessimistic (worst case) estimates to calculate expected value and account for uncertainty.
How is PERT estimate calculated?
PERT Estimate = (Optimistic + 4×Most Likely + Pessimistic) / 6. This weighted average gives more weight to the most likely estimate (4×) while accounting for best and worst cases. Example: O=10, M=15, P=25: Estimate = (10 + 4×15 + 25) / 6 = 15.83.
What is standard deviation in PERT?
Standard Deviation = (Pessimistic - Optimistic) / 6. This measures uncertainty and variability. Higher standard deviation = more uncertainty. Example: O=10, P=25: SD = (25 - 10) / 6 = 2.5. Use standard deviation to calculate confidence intervals and risk.
When should I use PERT?
Use PERT for: Project planning, task estimation, cost estimation, risk analysis, and any situation with uncertainty. PERT is especially useful when you have limited historical data or high uncertainty. It helps account for best-case, worst-case, and most-likely scenarios.