How FIDE Ratings Are Calculated
FIDE, the international chess federation, rates games with a simpler method than US Chess. There is no bonus, no second pass and no special formula for most players: a rating moves by a fixed K-factor times the difference between your score and FIDE's expected score. The details that matter are where the expected score comes from, which K applies to you, and how a first rating is set.
The formula
The expected score is read from FIDE's own published table of rating difference against scoring probability, rather than computed from a curve. It tracks the usual curve closely:
| Rating difference | Higher-rated player expects | Lower-rated player expects |
|---|---|---|
| 0 | 0.50 | 0.50 |
| 50 | 0.57 | 0.43 |
| 100 | 0.64 | 0.36 |
| 200 | 0.76 | 0.24 |
| 300 | 0.85 | 0.15 |
| 400 | 0.92 | 0.08 |
The 400-point rule
A difference of more than 400 points is counted as 400. So nobody is ever expected to score more than 0.92 against anyone, however weak the opponent. A 2000 beating a 1400 on K = 20 gains 1.6 rather than the 0.4 the true 600-point gap would give — four times as much. Since October 2025, players rated 2650 or above in standard chess use the real difference; the rule still applies to everyone else, and to everyone in rapid and blitz.
Which K applies to you
- K = 40 for your first 30 rated games, and for juniors (until the end of the year they turn 18) rated below 2300.
- K = 20 for most players.
- K = 10 once you have ever been rated 2400 or more. It never goes back up.
K times the number of games you play in one rating period may not exceed 700. A junior on K = 40 who plays 20 games in a month therefore has K cut to 35 for that period.
A worked example
A 1800 with K = 20 plays opponents rated 1850, 1750, 1900 and scores 1.5. Their expected scores are 0.43 + 0.57 + 0.36 = 1.36. The change is 20 × (1.5 − 1.36) = 2.8, which rounds to +3. Exact halves round away from zero.
Your first FIDE rating
You need at least 5 games against FIDE-rated opponents. Since March 2024, FIDE adds two imaginary draws against 1800-rated players to those games, then takes the average opponent plus a figure from its table for your percentage score. The two draws pull every first rating toward 1800:
| Results | First rating now | Without the two draws |
|---|---|---|
| Five games against 1400s, scoring 2.5 | 1514 | 1400 |
| Five games against 1800s, scoring 2.5 | 1800 | 1800 |
| Five games against 2000s, scoring 4 | 2101 | 2200 |
A weaker player is lifted and a stronger one held back. First ratings are capped at 2200, and any rating below 1400 is shown as unrated on the next list.
Performance ratings and the table's ceiling
The same table, read the other way, turns a percentage score into a rating gap — that is how a performance rating is worked out:
| Score | Performance above the average opponent |
|---|---|
| 60% | +72 |
| 75% | +193 |
| 90% | +366 |
| 99% | +677 |
| 100% | +800 |
Up to about 84% the table matches the textbook curve within five points. Above that it is deliberately cautious: at 99% it gives 121 points less than the curve, and a perfect score is capped at +800, because a short run of wins cannot show how much stronger someone really is.
To try your own event, open the FIDE Estimator. Source: FIDE Rating Regulations (Handbook B.02, effective 1 March 2024, amended 1 October 2025) and the Rapid and Blitz Rating Regulations.