Gaming Calculators
Elo rating change.
Enter two ratings, a K-factor and the result of the game to get each player's expected score and new rating with the standard Elo formula. Runs in your browser; nothing is sent or stored.
Inputs
Result
Fill the form and press Calculate.
Worked example
Two players rated 1500 each have an expected score of 1 / (1 + 10^0) = 0.50. With K = 32, a win adds 32 x (1 - 0.5) = 16 points (to 1516) and the opponent loses the same. If a 1400 player beats a 1600 player, the expected score was 1 / (1 + 10^(200/400)) = 0.240, so the win adds 32 x (1 - 0.240) = 24.3 points.
How it works
Expected score E_A = 1 / (1 + 10^((R_B - R_A) / 400)) and new rating R_A' = R_A + K x (S_A - E_A), where S is 1 for a win, 0.5 for a draw and 0 for a loss. Both formulas are given in the Elo rating system - Wikipedia article, which also says an expected score is win probability plus half the draw probability, that a 200-point gap in chess gives the stronger player an expected score of approximately 0.75 (the exact formula gives 0.76), and that FIDE uses K = 40, 20 or 10 depending on a player's rating and experience.
Most online games do not publish their ranking formula. Matchmaking rating (MMR) in many games is a different or modified system, so this calculator shows how a true Elo system works, not what your game will give you. The two players' changes cancel exactly, which is a property of the plain formula only.
Sources: Elo rating system - Wikipedia. Each opened 2026-10-08.
Planning guide only, not professional advice. Figures are estimates from the inputs you enter.
FAQ
What is the Elo rating formula?
The expected score is 1 / (1 + 10^((opponent - you) / 400)), and the new rating is your old rating plus K x (result - expected score).
What K-factor should I use?
Use the K your game or federation specifies. FIDE chess uses 40 for new and young players, 20 for players under 2400 and 10 for players at 2400 and above.
Does a 100-point rating gap mean a 64% win chance?
It means an expected score of about 0.64, which is win probability plus half the draw probability. In games without draws it equals the win probability.
Is my game's MMR the same as Elo?
Not necessarily. Many games use their own or modified systems and do not publish them, so the points you see can differ from this calculator.
Why do upsets give more points?
Beating a higher-rated opponent was unlikely, so the result minus the expected score is large. Beating a much weaker opponent gives few points.