Calculate Elo rating changes and win chances
The Elo system turns a rating gap into an expected score and moves both ratings after every game by how much the result beat or missed that expectation. This Elo calculator shows your expected score and win chance against an opponent, both players’ new ratings after a win, draw or loss, and the change for every possible result.
It is built for chess — with the FIDE K-factors and FIDE’s 400-point rule as options — and works just as well for any game or league that uses classic Elo. A multi-game mode totals a tournament or an evening of games in one go.
How to use the Elo calculator
- Enter your rating and your opponent’s rating.
- Pick the result: win, draw or loss.
- Choose a K-factor preset (FIDE 40, 20 or 10, or a common 32) or type your own. Untick Same as mine to give your opponent a different K.
- Tick FIDE rules to apply the 400-point rule and the K × games limit.
- For a tournament, open Several games and enter one opponent rating and result per line.
Elo Rating Calculator features
Expected score and win chance
From the rating gap, with a curve showing where you sit.
Both new ratings
Your change and your opponent’s, each with their own K-factor.
Win, draw and loss table
See what each result would do before you play.
FIDE options
K = 40 / 20 / 10 presets, the 400-point rule and the K × games cap of 700, with dates and sources.
Multi-game totals
Paste a list of games and get the combined change, with bad lines flagged.
The Elo formula
Expected score: E = 1 ÷ (1 + 10^((opponent − you) ÷ 400)). New rating: new = old + K × (S − E), where S is 1 for a win, 0.5 for a draw and 0 for a loss. For several games, add up S − E for each game and multiply by K once.
Example: a 1500 player beats a 1700 player. E = 1 ÷ (1 + 10^0.5) = 0.240, so the win was worth 1 − 0.240 = 0.760 of a point more than expected. With K = 20 the gain is 20 × 0.760 = +15.2, and the opponent loses the same 15.2 if their K is also 20. A draw between equal players changes nothing; a 400-point gap gives the stronger player an expected score of about 0.91.
FIDE K-factors and rules
Source: FIDE Rating Regulations (FIDE Handbook B.02), applied from 1 March 2024, read on 19 October 2026. If K multiplied by the number of games in a rating period exceeds 700, K becomes the largest whole number for which K × games does not exceed 700. Since 1 October 2025 a rating difference of more than 400 points counts as 400 for players rated below 2650; for players rated 2650 and above the real difference is used.
FIDE reads the expected score from its own table of rounded probabilities rather than the formula, so an official change can differ from this calculator by a fraction of a point. Rules change — check the current handbook for anything official.
| K-factor | When FIDE uses it |
|---|---|
| 40 | A player new to the rating list until they have completed 30 games; and all players until the end of the year of their 18th birthday while rated under 2300 |
| 20 | While a player’s rating stays under 2400 |
| 10 | Once a published rating has reached 2400, even if it later drops below |
Expected score, win chance and draws
Elo predicts points, not wins. An expected score of 0.64 means you should score 64 % of the points over many games — through wins, draws or a mix. In games without draws that is the win chance; with draws (common in chess), the actual chance of winning is lower than the expected score. The tool labels the percentage as the win chance if there were no draws for that reason.
Every 400 points of advantage multiplies the odds by 10: at +400 you expect about 10 points for every 1 your opponent scores.
Elo in online games
Many games and sites use Elo-like systems (often called MMR) with their own twists — different K values, rating floors, Glicko-style uncertainty or hidden ratings — so this calculator gives the classic Elo answer, not any particular game’s. Use the win rate calculator to plan a win streak, or practise on the chess board.
Elo Rating Calculator FAQ
How is Elo rating calculated?
Expected score E = 1 ÷ (1 + 10^((Rb − Ra) ÷ 400)); new rating = old + K × (score − E), with score 1, 0.5 or 0.
How many points do I get for beating a higher-rated player?
K × (1 − E). Against someone 200 points higher, E = 0.24, so with K = 20 you gain about 15.2 points.
What K-factor does FIDE use?
40 for new players (first 30 games) and for juniors under 2300 until the end of the year they turn 18, 20 below 2400, and 10 once you have reached 2400 (regulations applied from 1 March 2024).
What is the win chance with a 100-point gap?
The stronger player’s expected score is 1 ÷ (1 + 10^(−0.25)) = 0.64, so about 64 % of the points.
Why does my official rating change differ slightly?
FIDE uses a rounded probability table and rounds the final change, and other federations and sites use their own variants of the formula.
Does the 400-point rule still apply?
Yes for players rated below 2650: since 1 October 2025 a gap of more than 400 points counts as 400. Tick FIDE rules to apply it.