Chess Elo Rating Calculator

1. Enter your current Elo rating.
2. Enter your opponent current rating.
3. Choose the result: a win, a draw or a loss for you.
4. Pick your K-factor, then read your new rating, the points changed and your win probability.

An Elo rating is a single number that estimates a player strength, used in chess and many other competitive games. It was created by physicist Arpad Elo and adopted by the world chess federation, FIDE, in 1970. The higher your rating, the stronger you are judged to be.

The system is comparative: your rating only means something relative to others. Beating a higher-rated player earns you more points than beating a weaker one, because the result was less expected.

1. Find your expected score from the rating gap: E = 1 / (1 + 10 to the power of (opponent minus you, over 400)).
2. Score the game: 1 for a win, 0.5 for a draw, 0 for a loss.
3. Subtract the expected score from the actual score.
4. Multiply by the K-factor and add to your old rating.

The 400 in the formula sets the scale, so that a 400-point gap makes the stronger player about ten times more likely to win. The K-factor controls how quickly ratings move.

You are rated 1400 and beat an opponent rated 1200. The gap makes your expected score about 0.76, so a win is close to what was predicted. With a standard K-factor of 20, you gain 20 times (1 minus 0.76), which is about 5 points, taking you to 1405. Had you lost, you would have dropped by around 15 points instead, because losing to a weaker player is a surprising, costly result.

The Rating Gap

The bigger the difference between you and your opponent, the more the expected score tilts, and the more a surprising result swings your rating.

The K-Factor

A larger K moves your rating faster. New and junior players often use 40, most players 20, and elite players 10, so established ratings stay stable.

The Result

A win, draw or loss sets your actual score at 1, 0.5 or 0, which is compared with your expected score to decide the points.

Beating the Odds

Upsets pay the most: beating a much stronger player can earn close to the full K-factor, while beating a much weaker one earns very little.

Different rating bodies use different K-factors depending on experience and level.

Online platforms such as Chess.com and Lichess use their own variants, but the core formula is the same.

After a Game

See exactly how a result changes your rating before it is made official.

Planning a Tournament

Estimate how many points you stand to gain or lose against a given field.

Understanding Matchups

Turn a rating gap into a clear win probability so you know the odds before you sit down at the board.

1. Confusing Rating with Skill Points

Elo is comparative, not a score of moves; it only measures you against other rated players.

2. Using the Wrong K-Factor

Applying a master K to a beginner, or the reverse, gives changes that do not match how the real system would score you.

3. Expecting Big Gains from Easy Wins

Beating a much weaker player barely moves your rating because the win was already expected.

4. Forgetting Draws Count as Half

A draw against a stronger player can still raise your rating, because half a point beats your expected score.

This calculator applies the standard single-game Elo formula exactly, so the numbers match the classic model. Official ratings can differ slightly because of body-specific rules.

Your new rating is your old rating plus the K-factor times the difference between your actual score and your expected score. A win scores 1, a draw 0.5 and a loss 0.

It is your predicted result from the rating gap: E = 1 / (1 + 10 to the power of (opponent minus you, divided by 400)). It also reads as your win probability.

The K-factor sets how much one game can move your rating. It is 40 for new and junior players, 20 for most players, and 10 for masters rated 2400 and above.

More than for an even game, because the win was unexpected. Beating someone far above you can earn close to the full K-factor in points.

Only if you were expected to win. Drawing a much weaker player loses a little, while drawing a stronger player gains a little.

A 400-point difference makes the stronger player about ten times more likely to win, giving an expected score near 0.91 for the favourite.

Yes. Variants of the Elo system rate players in many games and sports, from table tennis to video games, using the same core formula.

It uses the classic Elo formula. Those sites use related systems such as Glicko, so their point changes can differ slightly.

No. The calculator runs entirely in your browser and nothing you enter is stored or sent anywhere.

• The Elo rating system (Wikipedia).
• Chess rating systems (Wikipedia).
• FIDE world chess federation (Wikipedia).