Longest Path vs Total Float ≤ 0: Understanding True Criticality

Critical path analysis is at the heart of planning — but not all planners fully understand the difference between Longest Path and Total Float ≤ 0 in Primavera P6.

Total Float ≤ 0

• Shows activities with no float or negative float

• Useful for identifying schedule compression

• Helps locate contractual delivery pressure points

However, it can mislead when calendars vary or constraints distort float.

Longest Path

• Tracks the actual driving sequence of activities leading to project completion

• Ignores float distortions

• More accurate for identifying true critical activities

• Preferred by forensic schedulers and claims professionals

When to Use Each

Purpose	Best Method
True critical path?	Longest Path
Contractual float reporting?	Total Float ≤ 0
Delay analysis?	Longest Path + change tracking
Executive reporting?	Longest Path

Understanding this difference is essential for producing defensible, dispute-proof schedules.