PlanningRule

Ninety-Ninety Rule

The first 90% takes 90% of the time. Finishing the rest takes another 90%.

A plain-language paraphrase. Original sources below.

The idea behind it

This joke about estimation is attributed to Tom Cargill and was popularized by Jon Bentley. Visible progress is a poor measure of remaining effort: integration, edge cases, testing, and release work often arrive late. Treat “almost done” as a prompt to list what remains, not as a reliable forecast.

Go to the source

Ninety-Ninety Rule — The Jargon File

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