How to Calculate the Earlies and Latest Time on Activity on Arrow

EARLY START (ES)

The earliest date a task can start.

EARLY FINISH (EF)

The earliest date a task can be completed

LATE START (LS)

The latest date a task can start without delaying the project end date

LATE FINISH (LF)

The latest date a task can finish without delaying the project end date

Calculate the Earliest Time

The calculation process begins with placing a zero in the Early Start (ES) position of the first activity. The rest of the calculation continues with the use of the following formulas:

Early Start = ES value from immediate Predecessor(s) + Duration.

Calculate the Latest Time

Calculate the latest times each task can start and finish without upsetting the project schedule, based on how long later tasks will take.

These are called the latest start (LS) and latest finish (LF).

Starting from the last task, where the latest finish is the project deadline, and working backward.

Latest start (LS): LF – Duration of the activity

How to calculate the earliest and latest time for Activity on Arrow