Example of a Duration Formula
If you have a task that is estimated to take 120 hours and you are paying $10 per hour, you need to budget $1200. However, the person is available only 75% of the time. Over a 6- to 12-month project, the project manager must allow for vacation, holidays, sickness, training, and so on. Assuming an average productivity of 80%, the duration is calculated as follows:
Duration = Effort/Productivity
Availability
= 120/.80 = 150 = 200 hours
.75 .75
= 200 hours
8 hours/day
= 25 days (versus the original 15 days (120/8))
* Note: The formula to calculate the duration is the following: Duration equals effort divided by the average productivity and then divided by the availability of the person.