Elo Rating Calculator (Chess and Games)
Enter both ratings, the result and the K-factor to see the new ratings.
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Elo Rating Calculator (Chess and Games) by TheCalcTools
How the Elo Rating Calculator (Chess and Games) works
The Elo system predicts each player’s expected score from the rating difference: a 400-point gap means the stronger player is expected to score about 91%.
After the game, each rating moves by K × (actual score − expected score). Beating a stronger player gains more points than beating a weaker one. The opponent’s change is the mirror image when both use the same K.
The formula
Worked example
Using the default values shown in the calculator:
| Your rating | 1650 |
|---|---|
| Opponent's rating | 1800 |
| Result | Win |
| K-factor | 20 (standard, FIDE under 2400) |
- Expected score: 1 ÷ (1 + 10^(150 ÷ 400)) = 0.297.
- A win changes the rating by 20 × (1 − 0.297) = 14.1, to 1,664.1.
Result:
| Your new rating | 1,664.1 |
|---|---|
| Rating change | 14.1 |
| Your expected score | 0.297 |
| Opponent's new rating | 1,785.9 |
| Win expectancy | 29.7% |
Frequently asked questions
Which K-factor should I use?
FIDE uses 40 for new players, 20 for most players and 10 for players who have reached 2400. Online sites and other games use their own values.
Why is my change not the same as my opponent's?
If you have different K-factors, the changes differ. With equal K, one player gains exactly what the other loses.
Sources and further reading
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This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.