Elo calculator
This Elo calculator uses the plain Elo formula. Enter your rating, your K-factor and each opponent's rating with your result. It shows your expected score (a 200-point favourite expects about 76%) and your rating change: K times the difference between what you scored and what you were expected to score.
Your games
- 1
Result
Enter your rating to start.
How it is calculated
- Expected score against one opponent = 1 / (1 + 10^((their rating − your rating) / 400)).
- Add the expected scores of all your games, and add up your points (1 for a win, ½ for a draw).
- Rating change = K × (points − expected). A higher K makes the rating move faster.
- Federations build on this with their own tables, K rules and rounding: use the FIDE, US Chess or ECF calculator for those.
Questions
- Which K should I use?
- It depends on who rates the game. FIDE uses 40, 20 or 10; the ECF uses 20 (40 for rising juniors); US Chess uses a sliding K from your game count. Online sites use their own systems. For a quick estimate, 20 is a reasonable choice for an established player.
- What does a 100-point rating difference mean?
- The higher-rated player is expected to score about 64%. At 200 points it is about 76%, and at 400 points about 91%.