Your rating is a single number that estimates how strong you are. Beat a stronger player and it goes up a lot; beat a weaker one and it barely moves; lose, and the same works in reverse. Over time it settles around the level you really play at. This page explains exactly how Chess Thrill calculates it — with the real numbers.
Chess Thrill uses Glicko-2, a rating system devised by the statistician Mark Glickman. It is an improvement on the older Elo system that FIDE still uses for over-the-board ratings, and it is used, in one form or another, by several major chess sites.
The key difference is that Glicko-2 does not just keep a rating for you. It also keeps track of how sure it is about that rating, a number called the rating deviation. When the system knows little about you, your rating moves a lot after each game, because every result tells it something new. As it learns more, your rating steadies.
Every new player starts at 1500, with a high deviation — in other words, the system has no idea yet how strong you are. That is why your first few games can move your rating by well over a hundred points, up or down.
Here is what that looks like, calculated with the same code that runs on Chess Thrill. Take a win against an opponent of exactly your rating:
| When | Points for the same win |
|---|---|
| Your very first game | about +175 |
| After thirty games | about +17 |
Same opponent, same result, ten times less movement. The first win moves your rating a lot because it is the first piece of evidence; the thirty-first barely changes what the system already knows.
While your rating is still uncertain, Chess Thrill shows it with a question mark after it — 1560?, for example. The question mark disappears once your deviation drops below a set threshold, which for most players takes about ten to fifteen games at that time control.
Ratings that still carry a question mark are left out of the leaderboards. A player who has won two games in a row can briefly have a very high rating, and it would be unfair to put that above players who have earned theirs over many games.
Once your rating has settled, what you gain or lose depends on who you played. Here is what one game does to an established rating of 1500:
| Result | Change |
|---|---|
| Beat a player rated 1900 | about +32 |
| Beat a player rated 1100 | about +3 |
| Lose to a player rated 1100 | about −32 |
| Lose to a player rated 1900 | about −3 |
A surprising result moves your rating a lot, and an expected one hardly at all. That is the whole idea: your rating only changes as much as the result was news.
There is also a safety limit. No single game can move a rating by more than 700 points, however unlikely the result.
You have a separate rating for every time control: one for 1-minute games, one for 3 minutes, one for 5 and one for 10. Many players are much stronger at slow chess than at fast chess, or the other way round, and one number could not describe both. A bad evening of bullet never touches your rapid rating.
Puzzles have a rating of their own too, calculated in the same way. Each puzzle counts as a game against the puzzle’s own rating: solving it without a mistake counts as a win, solving it with a single mistake counts as a draw, and using a hint or making two or more mistakes counts as a loss.
When you play another person, both ratings are updated at the end of the game, each one against the other player’s rating from before the game. That way neither of you is judged against a number that has already been changed by the result.
Games against our bots count for your rating too, as long as you are signed in. Each bot is treated as a player of its published rating, and because a bot’s strength does not change, the system treats that rating as well known. Beating a bot rated well above you earns you a lot; losing to one rated far below you costs you a lot.
There is one exception: the adjustable bot, whose strength you set yourself, does not affect your rating. Its strength changes from game to game, so there is no fixed rating to measure you against.
If you resign or leave a game before you have made your first move, it does not count for rating — for you or for your opponent. Clicking into a game by mistake, or closing the page straight away, should not cost anyone points. Once the game is properly under way it counts, and losing on time always counts.
A rating belongs to your account, not to your browser. If you play without signing in, your wins and losses are counted on that device, but you do not have a rating. Create a free account and your rating starts from your very next game.
A rating only means something next to other ratings from the same system and the same pool of players. A Chess Thrill rating, a FIDE rating and a rating on another chess site are three different measurements, and there is no simple way to convert one into another. The best use of your rating is to compare you with yourself: if it is going up, you are getting better.
Chess pieces: “cburnett” set by Colin M. L. Burnett, CC BY-SA 3.0.
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