What is Bottom-Up Estimating?

Bottom-up estimating prices every work package individually — ideally with the people who'll do the work — then rolls the numbers up through the WBS to a project total. It's the most accurate technique and the most expensive to produce, because it requires the full decomposition to exist first.

The hidden bonus: estimates built by the team are estimates the team owns. A number handed down from above is a target; a number built from below is a commitment.