# The coastline paradox and project estimation

### Estimating how much time a novel, complex project will take to complete can be as difficult as measuring a coastline. And measuring a coastline is surprisingly difficult.

“Geographical curves are so involved in their detail that their lengths are often infinite or more accurately, undefinable.”

Benoit Mandelbrot, How long is the coast of Britain?, 1967

”An example of the coastline paradox. If the coastline of Great Britain is measured using units 100 km long, then the length of the coastline is approximately 2,800 km. With 50 km units, the total length is approximately 3,400 km, approximately 600 km longer.”

Coastline paradox, Wikipedia

“Mandelbrot’s paper made clear that it’s all but impossible to answer the how-long question without first agreeing on a unit of measurement. Precision takes time which is why a trade-off needs to be made regarding the level of confidence needed and the time and resources required for the measurement.”

Andreas Holmer, Estimating Work: the Coastline Paradox

Update, June 2024. Related quote by Bertrand Russell:

”Everything is vague to a degree you do not realize till you have tried to make it precise, and everything precise is so remote from everything that we normally think, that you cannot for a moment suppose that is what we really mean when we say what we think.”