A colleague caught me off-guard the other day when he said he could calculate time.
It took me a minute, but I got it. He was referring to the PERT formula. Using 3 estimates, you can actually come pretty close to estimating the actual time to perform a task.
You need 3 estimates to make this work:
- The most optimistic (O) case when everything goes right
- The most likely (M) case considering the usual problems
- The most pessimistic (P) case when everything goes wrong
Use the PERT formula to calculate a “weighted average”.
(O + 4M + P) / 6
Just be sure to use consistent time values, that is, hours, days, weeks, months, etc.