Chess Rating Toolkit
Calculate Elo rating change and performance rating, plan what score you need before a tournament, and track your rating over time. Uses the FIDE formula, including the 400-point cap.
Not sure which K-factor applies?
FIDE: K=40 for new players and juniors under 2300, K=20 below 2400, K=10 once you have reached 2400. National federations (USCF, ECF, AICF) differ, so use Custom if you know yours.
Games
One game per line: opponent_rating result, result = 1, ½, 0 or W/D/L.
What do I need to score?
Enter the opponents you expect (or the field average repeated). We show your rating change for every possible score.
Expected score by rating gap
How the chess Elo formula works
Expected score is E = 1 / (1 + 10(Ropp − Rme)/400). Your change per game is K × (Score − E), where Score is 1 for a win, ½ for a draw, 0 for a loss.
Performance rating is the average opponent rating plus a difference from the FIDE conversion table for your score percentage.
Official changes depend on your federation's rules (rating floors, provisional ratings, rating-period updates), so treat results as accurate estimates.
New to this? Read the full guide to the rating toolkit.
Rating Toolkit FAQ
How is a chess Elo rating change calculated?
Your expected score is E = 1 / (1 + 10^((opponent - you) / 400)). Your new rating is old rating + K x (actual score - expected score). K is 40 for new players and juniors under 2300, 20 for most players, and 10 once you have reached 2400.
What K-factor should I use?
FIDE uses K=40 for players with fewer than 30 rated games and juniors under 18 rated below 2300, K=20 for players under 2400, and K=10 for players who have ever reached 2400. National federations and online sites may differ.
What is a performance rating?
Performance rating is the rating that matches your tournament score against the average rating of your opponents, using the FIDE conversion table. It estimates how strongly you played in that event.
Does the calculator work for FIDE, USCF and online ratings?
It uses the FIDE formula, which is the basis for most systems. USCF and Lichess or Chess.com (Glicko) ratings use different formulas, so results are an approximation for those.
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