E.Musk's definitions

Law of pi

In engineering, every task will take exactly 3.141592 times as long as initially anticipated. The Law of pi is therefore commonly used along project managers when they ask engineers how much time they think they need to finish their work.

Arjan: How long will it take you to finish the design of those tubes?
Vincent: about one and a half hour I think
Arjan: OK, so taking the Law of pi into account, that's gonna take you exactly 282 minutes

by E.Musk January 7, 2019