Elo Calculation: How Your FIDE Rating Changes After a Game

Your FIDE Elo rating changes in small steps after every rated game. The maths is simple but has a few details: the expected-score table, the K-factor and the 400-point rule. This article follows the FIDE Rating Regulations (2024, with the 2025 update of the 400-point rule).

1. Expected score

For each game take the rating difference (D) and read the expected score of the higher-rated player from FIDE's table: 0.50 for a difference of 0–3, about 0.57 at 50, 0.64 at 100, 0.76 at 200, 0.85 at 300 and 0.92 at 400. The lower-rated player's expectation is one minus that. A difference above 400 counts as 400 (except for players rated 2650 and above).

2. K-factor

K = 40: new players until they have completed 30 games, and all players until the end of the year of their 18th birthday while rated under 2300.
K = 20: players rated under 2400.
K = 10: players who have ever reached 2400.
If games × K exceeds 700 in a rating period, K is reduced.

3. The change

For each game compute (score − expected score), with 1 for a win, 0.5 for a draw and 0 for a loss. Add these up, multiply by K and round to the nearest whole number. Games against unrated opponents and unplayed (forfeited) games do not count.

Worked example

A 1500-rated junior (K = 40) plays a 1600-rated opponent. The difference is 100, so the expectations are 0.64 and 0.36. A win gives 40 × (1 − 0.36) = +25.6, a draw +5.6 and a loss −14.4. Against a 2000-rated opponent the difference would count as 400, the expectation would be 0.08 and a win would bring +36.8.

Your first rating

You need at least five games against rated opponents in FIDE-rated events, and your calculated initial rating must be at least 1400. It is based on your opponents' average rating plus two hypothetical 1800-rated opponents, adjusted by your performance. Classical, rapid and blitz ratings are kept separately.

Automatic calculator

Paste your chess-results link into the mytourneys Elo/UKD calculator: opponents and results are read automatically, your FIDE Elo and UKD change is shown round by round, with win/draw/loss scenarios for the next round. The calculation matches the FIDE changes published by chess-results exactly.

💡 For juniors with K = 40 every game matters: beating a strong opponent can bring up to +35 points, but losing to a weaker one costs just as much. Choose events where most opponents are a little stronger than you.