PERT Estimate Calculator

Summary

Enter optimistic, most likely, and pessimistic durations to get a PERT weighted estimate, standard deviation, and confidence range.

How it works

1. Enter the optimistic duration — the best-case time if everything goes perfectly.
2. Enter the most likely duration — your realistic day-to-day estimate.
3. Enter the pessimistic duration — the worst-case time if major problems occur.
4. Select the unit (hours, days, weeks, or months) for all three values.
5. The PERT expected duration is computed as (O + 4M + P) / 6.
6. Standard deviation is (P - O) / 6; the confidence range is Expected ± 3 × SD.

Use cases

• Estimate software development task durations more accurately than single-point guesses.
• Prepare project schedules with realistic buffer time baked in.
• Compare multiple tasks side by side using the multi-task table.
• Communicate uncertainty to stakeholders with a clear confidence range.
• Use in agile sprint planning to size stories with three-point estimates.
• Apply to construction, research, or any project with variable durations.
• Feed the expected value and variance into critical path analysis.
• Train team members on structured estimation techniques.

Frequently Asked Questions