PERT Distribution in Google Sheets
The project manager's secret weapon.
Interactive Sandbox
10,000 simulations running live in your browser.
When to use it
PERT (Program Evaluation and Review Technique) is a refinement of the Triangular distribution that uses a weighted mean — giving 4× weight to the most-likely value — to produce a smoother, more realistic bell-shaped curve. Developed by the U.S. Navy for the Polaris submarine program, it's now standard in project risk management and earned-value analysis. Use PERT over Triangular when your most-likely estimate is well-researched and the tails should be soft, not sharp.
- Earned Value Management (EVM) duration and cost modeling
- IT project sprint estimation with expert input
- Capital project scheduling in construction and engineering
- Supply chain lead time variability
How to build it
Native Sheets Formula
=BETA.INV(RAND(),(1+4*((ml-a)/(b-a))),1+4*((b-ml)/(b-a)))*( b-a)+a Using native RAND() requires you to copy this formula 10,000 times manually, which severely lags the browser.
The MonteSheet Way
MonteSheet uses a local browser engine to run 100,000 iterations in 4 seconds without writing a single formula.
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