A game of educated guesses
FermiUnlimited
You know more than you think.
How close can a good guess get?
One number at a time. Stay within 10× of the answer to keep your streak alive.
Checking the question bank…
Real source figures. Explicit assumptions. Every answer explained.
A little reasoning goes a long way
Turn a big question into a small calculation.
Make an estimate, compare it with a worked answer, and learn which assumption mattered. Keep landing within a factor of ten to build your streak.
Find a starting point
Read the units and picture a few quantities you already know.
Build an estimate
Break the question into parts. Use the calculator when a rough calculation helps.
Compare in ratios
Twice too big and half too small are equally close. Within ten times, you survive.
Learn and continue
Read the source figures and arithmetic, then keep the streak going with another question.
A few things to know
What counts as a surviving guess?
A positive estimate from one tenth to ten times the worked answer survives, including the endpoints. A factor of 1.1 or less is a Bullseye; a factor of 2 or less is Close. Your score is the number of consecutive questions you survive.
How do I enter a large number?
You can type 12000, 12k, 1.2 million or scientific notation like 3e6. Commas are accepted. The calculator supports brackets, ordinary arithmetic and powers, and lets you transfer a positive result to the answer field.
Where do the answers come from?
Each question includes its sources, assumptions and arithmetic. Some use rounded published facts, some calculate quantities from NASA or Natural Earth source data, and everyday models explicitly state illustrative assumptions. Model answers are useful estimates, not a claim that every real situation has that exact value.
Is there a timer or a daily limit?
There is no timer and no daily restriction. Think through a question for as long as you like. Questions cycle through categories and avoid recent repeats; you can begin a fresh run whenever you want.
Does my streak save?
The active question, current results, streak and best score save in this browser when storage is available. Refreshing restores the run. If browser storage is blocked, the game still works for the current session.
Is this the original Fermi game?
This is an independent remake inspired by the estimation gameplay of Fermi. Its question bank, explanations, artwork and code are created for this site. It has no connection to the original game’s creators or leaderboards.