Chess Elo Calculator
How many rating points will you win or lose? Enter your rating, then each opponent's rating and your result. Works for one game or a whole tournament.
K 20: the FIDE value for most adult players rated under 2400.
Good to know: ChessHost runs tournaments (pairings, results and standings), but it does not track or submit ratings. Official ratings are kept by FIDE and national federations, and online ratings by sites like chess.com and lichess. This calculator is an estimate for your own curiosity, so your federation's published number is always the one that counts.
What is this?
Most chess ratings are built on the Elo system, named after Arpad Elo. The idea is simple. Before a game, the rating gap says how many points you are expected to score. After the game, your rating moves by how much better or worse you did than that expectation.
Beat a stronger player and you gain a lot, because nobody expected it. Beat a much weaker player and you gain only a little, because everyone expected it. Lose to someone weaker and it hurts. This calculator does that sum for you, game by game, and adds it up for a whole event.
How to use it
- Type your current rating at the top.
- Pick your K-factor. Not sure? Read the table below, most adults use 20.
- Add one row per game: your opponent's rating, then tap W for a win, D for a draw or L for a loss.
- Read your rating change, your new rating and your performance rating. Each row also shows what that single game was worth.
How Elo is calculated
There are two steps. First, your expected score against one opponent:
Then your rating change for that game:
Your score is 1 for a win, 0.5 for a draw and 0 for a loss. For a tournament, FIDE adds up the change from every game and applies it at once, which is exactly what this tool does.
Which K-factor is mine?
| K | Who gets it under FIDE rules |
|---|---|
| 40 | New players until they have 30 rated games, and players under 18 (to the end of the year they turn 18) while rated below 2300 |
| 20 | Everyone else while their rating stays under 2400 |
| 10 | Players whose published rating has reached 2400, from then on |
| Custom | Other systems: many national federations and clubs pick their own K, so use theirs |
FIDE also has a cap for players who play a lot in one rating period: if K times the number of games goes over 700, K is lowered so it does not. And since 1 October 2025, the 400 point rule applies only to players rated below 2650. Those details come from the FIDE rating regulations, so check your federation's own rules if you are not FIDE rated.
Worked example
Sam is rated 1500 with K 20 and plays a three round weekend event:
| Opponent | Result | Expected | Change |
|---|---|---|---|
| 1600 | Win | 0.36 | +12.8 |
| 1450 | Draw | 0.57 | -1.4 |
| 1700 | Loss | 0.24 | -4.8 |
Sam was expected to score about 1.17 points and actually scored 1.5. That is 0.33 more than expected, times K 20, so Sam gains about 6.6 points and goes to roughly 1507. The average opponent was 1583 and Sam scored exactly 50%, so the performance rating is 1583. These are the numbers the calculator shows when the page loads.
Frequently Asked Questions
How is Elo calculated in chess?
First work out your expected score against the opponent: 1 / (1 + 10^((their rating - your rating) / 400)). Then take your real score (1 for a win, 0.5 for a draw, 0 for a loss), subtract the expected score and multiply by your K-factor. That is your rating change. For a tournament, add up the changes from every game.
What is the K-factor in chess?
The K-factor decides how big your rating swings are. FIDE uses 40 for new players until they have 30 rated games, and for players under 18 while they stay below 2300. It uses 20 for everyone else under 2400, and 10 once your published rating has reached 2400. A bigger K means faster movement up and down.
How much Elo do you gain for a win?
Against someone with the same rating you are expected to score half a point, so a win earns half your K-factor: +20 with K 40, +10 with K 20 and +5 with K 10. Beat someone rated higher and you gain more. Beat someone much weaker and you gain very little, because the win was expected.
What is a performance rating in chess?
A performance rating is the rating you played like in one event. Score 50% and your performance equals the average rating of your opponents. Score more and it goes above that average, score less and it goes below. This calculator gives a close estimate using the same Elo curve, capped at 800 points above or below the average.
What is the 400 point rule in FIDE ratings?
Under the FIDE rating regulations, effective from 1 October 2025, if you are rated below 2650 a rating gap of more than 400 points is counted as exactly 400. Players rated 2650 and above use the real difference in every case. The rule stops a huge gap from making a win almost worthless or a loss almost free.
Why is my chess.com or lichess rating change different?
Chess.com and lichess do not use plain Elo. They use Glicko style systems, which also track how sure they are about your rating, so new or inactive players move faster. This calculator uses the classic Elo formula, the same family FIDE and many national federations use for over the board play.
Does ChessHost track Elo ratings?
No. ChessHost runs the tournament itself: pairings, results, standings and tiebreaks. It does not keep or submit ratings. Official ratings come from FIDE and national federations, and online ratings from sites like chess.com and lichess. This calculator is a free side tool so you can estimate your own change.
Tied on points at the end? Try the chess tiebreak calculator. Planning an event? The Swiss rounds calculator tells you how many rounds you need. New to tournaments? Read how to enter your first chess tournament, how to prepare for a chess tournament and our Swiss pairing system guide.
Running the event yourself?
ChessHost does the pairings, results and standings for your club or school tournament. Players join by QR code. Create a free account and go, no credit card.
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