This process estimates the number of work periods each activity needs, based on scope, resource requirements, and historical data. The team chooses estimating techniques — analogous, parametric, three-point, bottom-up — and records not just the numbers but the basis of estimates, so the assumptions behind them stay visible.
Good estimates express uncertainty as a range rather than a single point, and reserve analysis sets aside contingency for known risks. The PM avoids treating an estimate as a commitment until it has been validated against resources and dependencies.
Common pitfalls. Single-point estimates that hide uncertainty; padding buried inside estimates instead of explicit reserves; ignoring resource availability and productivity; and reusing analogous estimates from genuinely different work.
Inputs, Tools & Techniques, and Outputs
Inputs
- Project management plan
- Project documents
- Enterprise environmental factors
- Organizational process assets
Tools & Techniques
- Expert judgment
- Analogous estimating
- Parametric estimating
- Three-point estimating
- Bottom-up estimating
- Data analysis
- Decision making
- Meetings
Outputs
- Duration estimates
- Basis of estimates
- Project documents updates