PERT Calculator

PERT estimates a task's duration by weighting three scenarios.

How the Math Works

The PERT calculator uses a weighted average formula to estimate task duration, combining optimistic (O), most likely (M), and pessimistic (P) time estimates. The expected time (E) is calculated as (O + 4M + P)/6, giving four times more weight to the most likely scenario. The standard deviation (SD) is derived from (P - O)/6, representing the spread between best-case and worst-case outcomes, which quantifies uncertainty in the estimate.

Practical Applications

This tool is ideal for project managers and planners to forecast task completion times in complex projects. By inputting optimistic, most likely, and pessimistic durations, users can prioritize tasks, allocate resources efficiently, and identify potential bottlenecks. The standard deviation helps assess risk, guiding contingency planning and ensuring realistic timelines for critical project milestones.

Day-to-Day Use

In everyday scenarios like planning home renovations, event setups, or learning new skills, PERT helps set achievable deadlines. By estimating best-case, most plausible, and worst-case timelines, users can prepare for delays, budget time effectively, and reduce stress from unrealistic expectations. It transforms uncertain tasks into structured plans, making personal and professional goals more manageable.

Worked example

O 4, M 6, P 12 give an expected 6.67 with SD 1.33.

FAQ