Win chance by rating difference
FIDE doesn't use a formula for the expected score. It uses its own table (8.1.2 in the Rating Regulations), and this calculator uses that table, so its numbers match FIDE's to the hundredth. An expected score of 0.64 means 64 points from 100 games, counting a draw as half a point, so it is a chance to score rather than a chance to win.
| Rating difference | Higher-rated player | Lower-rated player |
|---|---|---|
| 0 | 0.50 | 0.50 |
| 25 | 0.53 | 0.47 |
| 50 | 0.57 | 0.43 |
| 75 | 0.60 | 0.40 |
| 100 | 0.64 | 0.36 |
| 150 | 0.70 | 0.30 |
| 200 | 0.76 | 0.24 |
| 250 | 0.81 | 0.19 |
| 300 | 0.85 | 0.15 |
| 350 | 0.89 | 0.11 |
| 400 | 0.92 | 0.08 |
| 500 | 0.96 | 0.04 |
| 600 | 0.98 | 0.02 |
| more than 735 | 1.00 | 0.00 |
How FIDE works out a rating change
For each game against a rated player, FIDE looks up your expected score from the gap between your ratings. A gap of more than 400 counts as 400, unless you are rated 2650 or more in standard chess (since 1 October 2025); on the rapid and blitz list it counts as 400 for everyone. Your score in the game (1, half or 0) minus the expected score is that game's result against expectation. Add those up over the month, multiply by K, and round to the nearest whole number, with a half rounded away from zero.
K is 40 for a new player until they have 30 rated games, and for anyone under 2300 until the end of the year they turn 18. It is 20 for everyone else under 2400, and 10 for good once a player's published rating reaches 2400. If K times the number of games in a month would pass 700, K drops to fit, and the calculator does that by itself. FIDE's own rules are in the Rating Regulations in the FIDE Handbook (B.02, in force from 1 March 2024), read for this page on 19 October 2026.
This is for FIDE ratings. National federations and online sites have their own systems, and a first FIDE rating is worked out differently, from the average of your opponents.
Keep a record of every game
Chess Clock & Scorepad, our free app, keeps the clock and the scoresheet for over-the-board games, saves every finished game with its result, and shows two players' head-to-head record once both names are typed. Share any game as PGN when you want to look at it again.
Download on the App Store ▶ Get it on Google Play
More for over-the-board games:
More calculators:
Frequently asked questions
How is Elo calculated in chess?
For each game you get an expected score from the rating gap: 0.5 against an equal player, 0.64 against someone 100 points lower. Take your real score minus the expected one, add those up over the games, and multiply by K. Beat a player 100 points above you at K 20 and you gain 20 × (1 − 0.36) = 12.8 points.
How is FIDE rating calculated?
The same way, with FIDE's own table for the expected score instead of a formula. FIDE adds up every rated game you play in a month, multiplies by your K, rounds to a whole number and publishes the new rating on the first day of the next month.
How much Elo do you gain per win in chess?
Against an equal opponent, half your K: 10 points at K 20, 20 at K 40 and 5 at K 10. Beating a stronger player gains more and a weaker one less, down to almost nothing when the gap is large. A draw against an equal player changes nothing.
What is the K factor in FIDE ratings?
It's how far one game can move your rating. FIDE uses 40 for a new player's first 30 games and for juniors under 2300 until the end of the year they turn 18, 20 for everyone else under 2400, and 10 once a player has had a published rating of 2400.
What is the FIDE 400 point rule?
A rating gap of more than 400 points is counted as 400, so a win against a much weaker player still gains a little. Since 1 October 2025 the rule no longer applies to players rated 2650 or more in standard chess: they use the real gap. In rapid and blitz it still applies to everyone.
What is my win chance against a higher rated player?
FIDE's table gives an expected score rather than a win chance: 100 points below, you are expected to score 0.36 a game, which is 36 points out of 100 counting a draw as half. At 200 below it is 0.24 and at 400 below 0.08. The table further down has the rest.
Does Chess.com or lichess use Elo?
Not quite. Both use Glicko systems, which also track how sure they are of your rating, so the numbers move differently and don't match FIDE's. This calculator follows FIDE's rules; it will give a rough idea for an online rating but not the exact change.