Free tool
Chess Elo rating calculator
Two ratings in, what a game is worth out.
K is how far one game can move a rating. FIDE uses 40 for new players, 20 for most, and 10 once a rating has reached 2400. Online sites rate differently, so use this for over-the-board and club ratings.
Your expected score
29.7%
A win counts 1, a draw a half, a loss 0.
- If you win+14.1→ 1514.1
- If you draw+4.1→ 1504.1
- If you lose−5.9→ 1494.1
What it does
- Your chance of scoring against any opponent, from the two ratings.
- What a win, a draw and a loss would each do to your rating.
- FIDE's K-factors of 40, 20 and 10.
Questions
How is the expected score worked out?
From the gap between the two ratings, on the curve Elo's system uses: equal ratings give 50%, a 100-point edge about 64%, 200 points about 76%, and 400 points about 91%. A draw counts as half a point, so the expected score is a chance of scoring, not only a chance of winning.
What is the K-factor?
It is how far a single game can move your rating. FIDE uses 40 for players new to the rating list, 20 for most players, and 10 once a rating has reached 2400. A bigger K means bigger swings.
Does this work for chess.com or Lichess?
Not exactly. Online sites use their own systems (Lichess uses Glicko-2, for example), which also track how certain a rating is, so one result moves it by a different amount. This calculator follows the classic Elo formula used for over-the-board and many club ratings.
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