Difference between top-down and bottom-up estimation? - Google Project Mgmt
Google Project Management Interview Question and Answers - Difference between top-down and bottom-up estimation?
Definitions:
Top-Down Estimation — begin with a high-level effort/cost estimate for the whole project (often from analogous projects or executive guidance) and break it down into phases or budgets. It’s a macro-level, fast approach used to set initial budgets or go/no-go decisions.
Bottom-Up Estimation — decompose the work into detailed work packages (WBS), estimate each piece, then roll those estimates up to create the total. It’s a micro-level, detail-driven approach used for execution planning and control.
Comparison:
