Fermidle

About Fermidle

Fermidle is a daily game of back-of-the-envelope estimation. Each day at midnight a new question appears, such as how many red cars are registered in Cologne, and you get one guess with no take-backs.

Scoring is about orders of magnitude rather than precision. An exact answer scores 100 percent, being three times off scores about half, and being ten times off scores nothing. Alongside your number you can write out the reasoning that got you there; the game's automated judge checks it step by step and can raise your rating gain by up to one and a half times.

Players have an ELO-style rating that starts at 1500, like chess. Each question has its own difficulty rating, so beating a hard question earns more, and a streak counter rewards coming back every day.

It suits people who like estimation puzzles and want to practise structured reasoning, not just guessing.

How to play Fermidle

1. Open Fermidle and press Play today's Fermidle.
2. Read the question and break it into quantities you can estimate.
3. Optionally write out your reasoning step by step.
4. Enter your single final number.
5. See the answer, your accuracy and your rating change.

Screenshots

Tips

• Chain a few rough factors (population, share, rate) rather than guessing the total directly.
• Being within a factor of three still scores about half, so aim for the right scale first.
• Write your steps clearly if you want the reasoning bonus.

Questions