Ninety-ninety rule

Computer Science Concepts

The ninety-ninety rule is a humorous aphorism in computer programming and software engineering. It says that the first 90 percent of code takes the first 90 percent of development time, while the remaining 10 percent takes the other 90 percent. The rule refers to projects overrunning their schedules because difficult and unpredictable work is not anticipated. It is attributed to Tom Cargill of Bell Labs and was popularized by Jon Bentley in 1985.

The picture on this card was made with AI. It is an illustration, not a real photo of the subject.

Type: Humorous aphorism
Attribution: Tom Cargill of Bell Labs
Popularized by: Jon Bentley's September 1985 "Programming Pearls" column

Sources and credits

Article: Ninety–ninety rule (English Wikipedia)
Wikidata: Q3269245
Text: Card text is adapted from the English Wikipedia article by an automated summary. Wikipedia content is available under CC BY-SA 4.0; see the article history for its contributors. CC BY-SA 4.0 · Article history and contributors
Illustration: AI-generated illustration. Not a photograph or documentary image. (model: gpt-image-2)
Popularity: 90 median daily views (Wikimedia Pageviews API (all-access, user agent))

Kosmora is not affiliated with or endorsed by the Wikimedia Foundation.