PERT Calculator for Construction Project Duration (3-Point Estimate)
Formula
Expected Time = (Optimistic + 4×Most Likely + Pessimistic) / 6
Governing Standard
PMI PMBOK Guide, PERT technique
Required Inputs
- Optimistic estimate O (days)
- Most likely estimate M (days)
- Pessimistic estimate P (days)
Output
Expected duration (days) and standard deviation
Notes
The PERT formula gives a weighted average that accounts for uncertainty. The standard deviation is (P-O)/6, which helps calculate confidence intervals. For a 90% confidence level, add 1.3× standard deviation to the expected time.
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