Agile & Delivery playbook/Module 5 · Estimation & forecasting

Day 49 / 100 · Estimation & forecasting · The cone of uncertainty

Early numbers are wide.

The earlier the estimate, the wider its honest range. The cone narrows only as the team learns by doing the work.

4× 0.25× ACTUAL

At the idea stage, estimates can be off by up to four times in either direction.

As you learn, the range narrows.

Only near the end is it tight.

Barry Boehm, 1981; popularised by Steve McConnell.

Source: Steve McConnell, Construx: Software Estimation's Cone of Uncertainty ↗

Early numbers are wide. Narrow them by learning.

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