Chess Rating Calculator FAQ

Because the Elo system expected you to score higher than 0.50 against that opponent. If your expected score was 0.75 (because you were the significant favorite), a draw at 0.50 underperformed the prediction by 0.25. Multiply that shortfall by your K-factor, and you get a negative rating change. The draw did not lose you points because draws are bad — it lost you points because the system expected you to win.

This is one of the most counterintuitive aspects of the Elo system, but it makes mathematical sense: a draw against a much weaker opponent provides evidence that your rating may be slightly too high, so the system corrects downward. Pour mieux comprendre la règle, lisez Edge cases and rounding.

Under current FIDE rules: K=40 if you have fewer than 30 rated games and have never reached 2400. K=20 if you have 30 or more games but have never reached 2400. K=10 if you have ever reached 2400, permanently. US Chess uses a different variable system based on game count and provisional status.

If you are unsure, K=20 is the most common value for established tournament players. Use our K-Factor Calculator to compare how the same result would affect your rating under all three K-factor bands side by side.

Rating change is how many points your existing rating goes up or down after an event. Performance rating is a standalone measure of how strong your play was in that specific event, calculated from your score against the field. They answer different questions: rating change tells you where your number ended up. Performance rating tells you how well you played.

A player can have a high performance rating but a small rating gain if their K-factor is low. Conversely, a modest performance rating can still produce a large point swing if K=40 applies.