HKSM

In critical path method scheduling, the EF is the earliest time the remaining work of an activity could complete, based on the network logic, the current data (status) date, and any schedule constraints.

Key Points

• Computed during the forward pass: EF = ES + activity duration, adjusted for calendars, lags, and constraints.
• Refers to the uncompleted portion of the activity and cannot be earlier than the data date for future or remaining work.
• EF values drive successor timing; a successor's ES depends on predecessor EFs and relationship lags/leads.
• On the critical path, early and late dates coincide (EF = LF), yielding zero total float.

Example

An activity "Design" has a 5-day duration, no predecessors, and the data date is Monday, May 5. Using a 5-day workweek calendar, ES = May 5 and EF = Friday, May 9. A successor "Build" with a finish-to-start relationship can begin the next working day after EF, which is Monday, May 12.

PMP Example Question

During a forward pass, how is an activity's Early Finish Date (EF) determined?

1. By subtracting total float from the Late Finish.
2. By adding the activity duration to the Early Start and applying calendars, lags, and constraints.
3. By taking the minimum EF of all successor activities.
4. By selecting the earliest date resources are available.

Correct Answer: B — Add duration to Early Start and account for calendars, lags, and constraints

Explanation: EF is a forward-pass calculation based on network logic and timing rules; it is not derived from float, successors, or resource availability alone.