Fermi Problems

I love Fermi problems and Fermithons as an activity, but when I go looking for problems, they’re surprisingly hard to find and scattered around.

Here are the resources I’ve collected over time. (I’d love to be able to add more, send them in!)

The Less Wrong Introduction is fantastic, and has a few worked examples
University of Maryland Fermi Problems Site has a few dozen in different categories but don’t have answers. Some easily googleable, others not.
Math With Bad Drawings has a few questions at the top with answers right there, so they’re good for others but very hard not to get spoiled on, then some cute Fermis but without answers

Guesstimation: Solving the World's Problems on the Back of a Cocktail Napkin - Lawrence Weinstein, John A. Adam, a book recommended by an Atlas Fellow, Kushal Thaman
Stupid Calculations seemed so promising but I can only find a few real examples on the site. The best ones (according to me) are in the post Drinking the Pool (he does all the calculations)
- Another good one is What if Instagram Pictures Were on Film?
I had remembered xkcd’s What If as being a perfect source of Fermis, but in practice I think you end up needing or needing to look up a lot of specialized knowledge, which I think makes it less fun. Nonetheless, I quite like Earth-Moon Fire Pole one. Probably there are others that fit the bill well.
Some good questions in these two resources for teachers, but no answers

Lots of elements in the Numbers Every EA Should Know deck that I like so much could be Fermi’d, and in fact when I don’t know an answer I usually do try to Fermi a first guess
Our World In Data, of course is an amazing source of interesting numbers

Not Fermi problems but great

A set of really charming estimation problems, where you have to guess / figure out how many or how long or etc. given a picture of a situation: Estimation 180
Strongly recommend having people guess the responses to Gallup polls, people do surprisingly badly.

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