Three-Point Estimating

Three-Point Estimating 150 150 CloudGovCo

I am often surprised how many project managers don’t know how to estimate. There are many #estimating methods, such as analogous, top-down, bottom-up, parametric, PERT, relative and three-point, and it’s useful to know them all. Here we discuss simple three-point. This takes the best guess (BG). which is the average amount of work the task might take if it were performed 100 times, the pessimistic (P) estimate if negative risks go wrong; and the optimistic (O) estimate if positive opportunities materialize. These values are simply averaged to derive the estimate (E).

E = (BG+P+O)/3

Sometimes this is weighted to the best guess in a PERT method:

E = (4BG+P+O)/3

A more sophisticated three-point estimate, such as this tool, would include an analysis of the standard deviation to give you a confidence level. At the end of the day, you have to use your experience, research and risk competence to select the best estimation.