Chess Elo Rating Calculator

See Exactly How Much a Game (or a Whole Tournament) Will Move Your Rating

Elo looks simple from the outside — beat someone rated higher, gain more points — but the actual formula involves an exponential expected-score curve that's hard to eyeball. This calculator runs the real FIDE-style Elo math: enter your rating, your opponent's, the result, and the K-factor that applies to you, and get your exact rating change and win probability. Switch to tournament mode to process a whole event's results game by game and see your rating move after each round, plus your performance rating for the event.

How to use it

• Enter your current rating and pick your K-factor — 40 for newer players with under 30 rated games, 20 for most adult players under 2400, or 10 for 2400+ (FIDE Masters and above).
• For a single game, enter your opponent's rating and the result to see your rating change and pre-game win probability.
• Switch to "Multiple Games" to add every round of a tournament — the calculator applies each result sequentially, updating your rating after every game, exactly like a real rating period.
• Tournament mode also shows your performance rating — roughly, the rating you'd need to have scored that result against that average opposition.

Real-world use cases

Checking before a big game how much you stand to gain or lose against a specific opponent, based on the rating gap. Estimating your new rating after a weekend tournament before the official results get processed and published. Understanding why beating a much lower-rated player barely moves your rating, while even a draw against a much stronger one gives a solid bump.

Frequently asked questions

How is chess Elo rating calculated?

Your expected score against an opponent is 1 / (1 + 10^((opponent rating − your rating) / 400)). Your new rating is your old rating plus K × (actual score − expected score), where actual score is 1 for a win, 0.5 for a draw, and 0 for a loss.

What K-factor should I use?

FIDE uses 40 for players new to the rating list (until they've completed 30 games), 20 for most players rated under 2400, and 10 once a player has reached 2400 and played enough rated games. Chess.com and Lichess use their own, generally higher K-factors for online blitz/rapid ratings.

Why did my rating barely change after beating a much weaker opponent?

Because you were already expected to win. The formula only rewards outperforming expectations — if your expected score was already 0.9 and you scored a full 1, the gap (and therefore the rating change) is small.

What is a performance rating?

It's an estimate of the rating level you played at during an event, based on your results against the average rating of your opponents. It's commonly used to describe a strong tournament result independent of a player's actual, slower-moving official rating.

Does a draw always help or hurt your rating?

It depends entirely on the rating gap. A draw against a higher-rated opponent usually gains you points (you scored above your expected value), while a draw against a much lower-rated opponent usually costs you points (you scored below what was expected).