PERT calculator
Give each task a best, likely and worst case. Get an estimate you can defend.
How to use it
- Pick hours or days.
- Add one task per row: the name, then best case, likely case, worst case.
- Read the expected time for each task and the project total, with a likely range.
- Press Show the formula to see the math.
The PERT formula
Expected = (best + 4 × likely + worst) ÷ 6
The likely case counts four times. The best and worst cases pull the answer a little toward them.
Example: a task could take 3 days at best, 5 most likely, 9 at worst. Expected is (3 + 20 + 9) ÷ 6 = 5.3 days.
The spread is (worst − best) ÷ 6. Here that is 1 day. A big spread means the task is not well understood yet.
Why the total is not just the sum of worst cases
If every task hits its worst case at once, the project is in deep trouble. That rarely happens. Some tasks run long, others finish early.
So PERT adds up the expected times, and combines the spreads in a way that lets the good and bad luck partly cancel. The result is a range, like 17.3 days, likely 15.3 to 19.4. That is much more honest than "17 days" and much tighter than adding every worst case.
Where M-Tracker fits
M-Tracker times each task, so next time your "likely" comes from what similar work really took. It also shows how much time went to redoing work. No screenshots and no activity tracking.
Make the estimate better
- Split big tasks. Anything over a week usually hides two or three tasks.
- Ask the person doing the work. Their likely case beats a manager's guess.
- Count review time. Work that comes back adds days PERT does not see unless you list them.
Try M-Tracker free14-day trial. No credit card. No employee surveillance.
Questions people ask
What does PERT stand for?
Program Evaluation and Review Technique. The US Navy created it in the 1950s.
Is PERT the same as a three-point estimate?
Close. A simple three-point estimate averages the three. PERT weights the likely case.
Is anything stored?
No. It runs in your browser.
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