Critical Path Example: Manually Calculating the Critical Path

The critical path example consists of demonstrating the forward and backward pass.

The Forward Pass

Calculates ES and EF times

Computes early event time for each node

Move left to right on the diagram below

1. Take the preceding activity early event time and add the duration

2. If more than one activity precedes it then the largest value is recorded

3. Write down trial values

Note the first node always has an early event time of 0

The Backward Pass

Calculates LS and LF times

Computes the late event time for each node

From right to left

1. Take the preceding Late event time and subtract duration

2. If more than one activity precedes it then the smallest value is recorded

3. Write down trial values

Activities are critical when:

1.Early Event Time & Late Event Time are the same

2.ES and LS & EF and LF time are the same

Applying these rules to our example the Critical Path is as follows:

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