Chess Elo Rating Update Calculator
Calculate your updated Elo rating after a chess game using the FIDE formula, expected score, and K-factor.
Results
What is it?
The Elo rating system quantifies relative skill between players using a logistic curve. Your expected score against an opponent is calculated as E = 1 / (1 + 10^((opponent - you) / 400)). Your rating then changes by K * (actual - expected), where K controls the sensitivity of rating changes.
How to use
Enter your current Elo rating and your opponent's. Select your game result (Win, Draw, or Loss) and your K-factor (K=40 for new players to allow rapid adjustment, K=20 for standard, K=10 for established high-rated players). The calculator shows your new rating and the change.
Example scenario
You are rated 1400, opponent is rated 1500 (K=20). Your expected score = 36%. If you WIN: new rating = 1400 + 20*(1-0.36) = 1413 (+13). If you LOSE: new rating = 1400 + 20*(0-0.36) = 1393 (-7). Beating stronger players gives more points; losing to weaker players costs more.
Pro tip
The 400-point gap in the formula means a player rated 400 above you should win 91% of games by expectation. FIDE uses K=40 for players under 18 or in their first 30 games, K=20 for players with a rating under 2400, and K=10 for established players rated 2400+. Online platforms like Chess.com and Lichess use similar but proprietary systems with faster adjustment.