Chess Elo Rating Calculator
Calculate your expected score and rating change after a game.
K = 10 / 20 / 40 depending on category
K factor used: 20. Your opponent gains the exact opposite change in the same game.
How the calculation works
The Elo rating system assumes that ratings predict results. Against a player of equal rating you are expected to score 0.5 (50%). The expected score formula is:
The rating change is then K × (actual score − expected score), where the actual score is 1 for a win, 0.5 for a draw, and 0 for a loss. Beat a much higher-rated opponent and you win a lot of points; lose to someone far below you and you lose a lot. A draw against a much stronger player is still a small gain for you.
K factors by rating system
- FIDE: the international rating list uses K=40 for players with fewer than 30 rated games, K=20 for players rated under 2400, and K=10 for players rated 2400 and above.
- Chess.com: its ratings change more slowly; a fixed K of 10 is the commonly cited approximation.
- Lichess: actually uses the Glicko-2 system, where the change depends on your rating deviation as well as the result. This calculator uses a K of 40 as a rough Elo equivalent for established accounts.
This calculator gives the Elo-style estimate used in the formula above. Online platforms do not expose their exact internal algorithms, so the numbers will not match a specific game's live rating change exactly. For a real-world check, analyze a player's actual rating history on the main tool and compare the trend.