How do you rank players who never all play each other? The Elo system turns a rating gap into a precise win probability — and updates it after every game.
Elo Rating SystemLive
who should win?
Player A
1600
64%
vs
Player B
1500
36%
Controls
Presets
The Elo system, born in chess and now everywhere from tennis to video games, turns a rating gap into a win probability. Every 400 points means a tenfold odds advantage. After each game, ratings shift by the K-factor times the surprise — beating a much stronger opponent gains far more than beating a weaker one, and an upset costs the favorite dearly.
Reading this result: A is rated +100 vs B, a 64% win chance — every 400-point gap multiplies the odds tenfold. With K=32, a win nudges A by 12 but a loss costs -20, so beating a stronger foe pays far more than beating a weaker one.
Runs locally in your browser — free forever. Scale to the cloud when reality gets heavy.
★ Sign in to save this setupSave your tuned setup, or drop this simulation into your own site, docs, or course page.
How it works
Elo assigns each competitor a rating; the difference predicts the odds, with every 400 points meaning a tenfold advantage. After a match, ratings shift by the K-factor times the difference between actual and expected result, so upsets move ratings a lot and expected wins barely at all. It rates chess players, tennis pros, and video-game ladders alike.
✦
Ask the AI about this model
The math, the assumptions, real-world uses, or a code translation — explained for this exact simulation.
Yes. Elo Rating System runs entirely in your browser using your device's own compute, so local use is free forever. You only pay Compute Tokens if you scale a job to the cloud.
Do I need to install anything?▾
No. Everything runs client-side in a modern browser — no downloads, no license, no account required to start.
Can I save or share my simulation?▾
Create a free account to save projects, and use a shareable embed or minted DOI to publish a live, interactive version anywhere.
How accurate are the results?▾
The solver uses established numerical methods, but results are for research and educational purposes and should be validated against experiment or professional review before you rely on them.