Task Time Estimator

How to use this tool

1. Type the three estimates in the same unit (hours, days or minutes) — optimistic, most likely, then pessimistic.
2. Press Generate. The tool shows the PERT expected time, the standard deviation and the expected range.
3. Use Load sample for a 2 / 4 / 12 hour task, or Clear to start again.

Worked example

For optimistic 2 hours, most likely 4 hours and pessimistic 12 hours, the expected time is (2 + 4 x 4 + 12) / 6 = 5.00 hours, the standard deviation is (12 - 2) / 6 = 1.67 hours, so the likely range is 3.33 to 6.67 hours.

What this tool does not do / Limits

This is a planning estimate, not a promise: it assumes the three estimates are honest and in the same unit, and it requires optimistic at most most likely at most pessimistic. It does not account for dependencies, waiting time or other tasks.

Frequently asked questions