[ianmcgowan]

It's really hard. And strangely it can be easier to estimate a new project (that's similar to something you've done before) than optimization or bug fix projects. Known unknowns vs. unknown unknowns and all that.

Estimates in general are hard - I've had clients break everything down into micro chunks and estimate to the hour, and come up with a total ~100 hours. When I try to gently remind them that the last similar project took three months, there's generally push back. But if nothing changes in the approach, it generally takes about the same time.