Free chess calculator
A rating gap is a probability in disguise. Set the difference and your draw estimate to see your expected score, plain odds, and the full curve from underdog to favourite.
Positive means you're higher rated. The gap is the only thing that sets the odds.
Splits your expected score into outright wins and losses. Higher among stronger, closely-matched players.
The curve is an S, not a line: near equal ratings a few points barely move the odds, but out at ±400 the score is already about 91% / 9%. That's why upsets are rare but never impossible, and why rating points get harder to win the higher you climb.
Almost — the Elo formula gives an expected score (average points per game) from the rating gap. With a draw-rate estimate this tool splits that into separate win and loss chances, since a 60% expected score can be many wins and losses or lots of draws.
Because it's logistic. Near equal ratings the odds move slowly, but as the gap widens they saturate toward 100% or 0%. At about 400 points the score is roughly 91% to 9%.
Your win/draw/loss odds against any opponent, and exactly what a win, draw or loss does to your rating.
Your most likely total over N games at a given rating gap, plus the honest spread around it.
Turn a tournament score into the rating you actually played at — the number a good event is really worth.
Educational chess content. Rating math uses the standard Elo model; results are estimates and vary by federation, pool and time control.