Charlie Steiner answers What are some triggers that prompt you to do a Fermi estimate, or to pull up a spreadsheet and make a simple/​rough quantitative model?

[Charlie Steiner]

I do it pretty rarely, so maybe not the best answerer. But I often do it when I feel like I want to compare long-term plans and one of them has a clear price while the other one only maybe does. Trying to estimate prices I’d put on things is one of a couple different decision-making tools.