Time estimation using PERT

Although there certainly are more complex and structured ways of estimating time, there is a rather simple method to estimate time that has proven interesting to me in many scenarios: PERT.

Basically, you'll have to do 3 estimations for each task: optimistic (O), most likely (M) and pessimistic (P).

These estimations are obviously dependent on how you evaluate the hardness of a task and on the people (or profile) you believe will perform them. One of the most important steps here, is defining as much sub-tasks as possible. Be as granular as possible, so that nothing is forgotten or wrongly evaluated.

After doing your set of estimations for each task/sub-task, you should apply this formula to get the expected time (T_E):

T_E = (O + 4M + P) ÷ 6

Also,one of the most important things in time estimations, is to keep track of your own estimations and the time they really took. Nothing like a reality check to improve your estimations. One of the aspects that should be taken into account is the person who performed the task and their level of seniority.