How many light poles line the streets of a major city?

Fermi estimation is the art of reasoning your way to a rough answer for a question that seems impossible to look up, like how many piano tuners work in a city. You break the question into a few quantities you can guess, multiply them, and aim to land within the right order of magnitude.

Fermi Daily gives you one new estimation puzzle every day. Enter your best guess, see how close you were on a logarithmic scale, and compare your reasoning with a step-by-step walkthrough. Build a streak, replay past days in the archive, learn the method in the guide to Fermi questions, or study worked examples.