Home > Leadership, planning > The PI constant in software estimation

The PI constant in software estimation

Already in 1975, Fred Brooks suggested in Mythical Man Month, Fred Brooks that you should triple any developer estimation. And reading blog posts, talking to fellow project managers and stressed IT managers, we all know that this is still valid. At the same time all these project managers and IT managers have a hard time accepting this. But from now on, you can refer to the mathematical formula of estimation. We all know it.


Project Management Estimation = Software developer’s estimation * PI

Yesterday, we discussed this over lunch and one of the bright developers at TUI Nordic said it was the PI factor which wasn’t considered in project management.



If we see the problem as the circle we could say that we cover the problem by travelling from one end of the circle to the next. And that is what developers estimate. You could say that they are estimating the diameter.

But when they need to complete the task they have to take the route around the circle. Not only do they have to take a longer trip to reach the other side of the circle, they must also complete the whole circle and that was never in their estimate. You have setting up development environment, merging, build script problems and all that stuff which you never considered. That is the circumference of the task.

You cannot argue PI, can you?

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  1. 2011/11/29 at 8:39 pm

    Hello everyone,

    A french translation of this post is available here : http://tinyurl.com/cxtuwzn

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