ELO Rating Calculator
Calculate post-match ELO rating changes using the FIDE formula with adjustable K-factor for any competitive game.
Results
What is it?
The ELO system, developed by Arpad Elo for chess, quantifies player skill as a single number. Your expected score against any opponent is E = 1 / (1 + 10^((Rb-Ra)/400)). After the game, your new rating = old rating + K x (actual score - expected score). A win scores 1.0, draw 0.5, loss 0.0.
How to use
Enter your current ELO, your opponent's ELO, the match result, and a K-factor. The calculator shows your expected win probability, the rating change, and your new ELO. Use K=32 for most online games; K=40 for new accounts; K=10 for elite-level play.
Example scenario
You: 1500 ELO, Opponent: 1600 ELO, K=32, Result: Win. Expected score = 0.360, rating change = +20.5, new ELO = 1520. You gained more because you beat a stronger opponent. A loss would have cost only -11.5 points.
Pro tip
The 400-point rule: at a 400-point ELO difference, the stronger player wins about 91% of the time. Most online games use modified ELO (MMR systems) with additional factors like placement matches, win streaks, and hidden MMR. K=32 is the FIDE standard for players under 2400 with more than 30 games played.