6.4 Estimate Activity Durations

Estimate how long each activity will realistically take to finish.

Planning / Schedule · ← PMBOK reference · See it on the map

Why it matters

An optimistic guess here understates the whole schedule, and everything built on top of it — the finish date, the staffing plan — inherits that understatement.

What done looks like

Every activity carries a duration estimate with its basis and assumptions recorded.

First time tip

Give a range, not a single number, for anything you are not confident about. A range keeps the uncertainty visible instead of hiding it in one guess.

What you need (Inputs)

• Schedule Management Plan
• Activity List
• Activity Attributes
• Milestone List
• Risk Register
• Resource Requirements
• Resource Calendars
• Enterprise Environmental Factors

How you do it (Tools & Techniques)

• Expert Judgment
• Analogous Estimating
• Parametric Estimating
• Three Point Estimating
• Bottom Up Estimating
• Data Analysis

What you get (Outputs)

• Duration Estimates
• Basis of Estimates

Worked example

Repainting the reading room is three days for two painters, from the contractor's own rate. The wall repair is two to five days, because nobody has opened it yet — and that range is what keeps the doubt visible instead of buried in one number.

Common pitfalls

• Estimating the work and forgetting the waiting — drying, delivery, an inspection.
• Giving one confident number for the activity nobody has actually looked at yet.
• Shortening an estimate to fit a date that was promised before the estimate existed.

How driftless helps

• Analogous Estimating can be run here.
• Parametric Estimating can be run here.
• Three Point Estimating can be run here.
• Bottom Up Estimating can be run here.
• Basis of Estimates can be created in the wizard.