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. For a fuller explanation of the rule behind it, read 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.