Project Management Tool

PERT Calculator

Estimate project duration using optimistic, most likely, and pessimistic activity times. Calculate expected duration, variance, standard deviation, float, and the critical path.

PERT logic: Each activity uses three time estimates to calculate its expected duration and uncertainty. Expected Time (TE) = (Optimistic + 4 × Most Likely + Pessimistic) ÷ 6 Variance = ((Pessimistic − Optimistic) ÷ 6)²

Activity

Optimistic

Most Likely

Pessimistic

Predecessors

Expected project duration

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Critical path

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Project variance

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Project standard deviation

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PERT activity schedule

Activity	O	M	P	Expected Time	Variance	Std. Dev.	ES	EF	LS	LF	Total Float	Status

Completion probability

Target completion time (working days)

Enter a target duration to estimate the probability.

Interpretation

PERT probability uses the normal approximation: Z = (Target − Expected Duration) ÷ Project Standard Deviation.

Critical path timeline

How to use this PERT calculator

1. Add activities Enter each project activity and provide three time estimates.

2. Set predecessors Select every activity that must finish before the current activity can start.

3. Calculate PERT Review expected duration, uncertainty, float, and the critical path.