# Chess Ratings - How They Work

• erik
• | Aug 23, 2007
• | 198578 views

Like it or not, we ALL have a chess rating. You may not care at all about your rating, or you may be whining every time it goes down in the slightest. You might be someone who plays a game a year, or someone who plays 1,000 a day. Still, there is a number out there that represents how well you play chess. Well, that's the theory, anyway.

To understand chess ratings you have to understand two things: #1 - that you have a TRUE rating that perfectly represents your strength of play, and #2 - that that TRUE rating will never be known and so we have to use statistics to get as close as possible to the truth. I'm writing this article in response to many people who ask about ratings and need a simple explanation of how they work. (I only know about all this because of a recent super-in-depth statistics course I took and my research in building Chess.com!)

There are two main rating systems, and each one has its merits.

The Elo System (used by the United States Chess Federation, FIDE, and many other online chess sites) is popular for two reason - it has been around for a long time, and it is simple. The idea is this: given two chess players of different strengths, we should be able to calculate the % chance that the better player will win the game. For example, Garry Kasparov has ~100% chance of beating my 4-year-old daughter. But he may only have a ~60% chance of beating another Grandmaster. So when playing that other Grandmaster, if he wins 6 games out of 10, his rating would stay the same. If he won 7 or more, it would go up, and 5 of less, his rating would go down. Basically, the wider the spread of the ratings, the higher percentage of games the higher rated player is expected to win. So to calculate a person's rating after playing a few games you calculate the average ratings of his opponents, and then how many games he was expected to win, and then plug it into a formula that spits out the new rating. Simple enough. Well, it turns out, that is maybe TOO simple.

I wish there was some simple analogy to explain all this, but there isn't. It all comes back to this: you have a theoretically exact chess rating at any given moment, but we don't know what that is and so we have to use math to estimate what it is. There are really smart people out there who work on this stuff for a living, and at the end of it all we get to put their proven methods into our code so that we can all enjoy knowing what little numbers next to our name we deserve.

If you want to read more, check out these articles (WARNING - SEVERE NERD CONTENT AHEAD):

• 3 years ago

It happened several times. I was playing white and it was the opponent's turn. I made a move and waited for him to play. All of a sudden the game stopped and I got a msg black won. WHY?????

• 3 years ago

Just because I was interested, I found this discussion:

Rating Point Option on Timeout Wins

Part way down the discussion, TadDude says: "Timeouts where there are less than three and a half moves do not impact rating in any type of game."

• 3 years ago

No, it's not your imagination and neither is it a bug. It depends on how many moves are made in the game before the timeout. I can't remember exactly but I believe you need to have made at least 4 or 5 moves for the rating to change...

So, obviously your rating won't change if your opponent times out without any moves for example.

• 3 years ago

That's a good question. Recently, I've been noticing that my rating hasn't been changing when certain opponents timeout. I don't know if it's something to do with timeouts not counting if the opponent is still at the "Unrated" stage or whether it's a bug or whether it's just my imagination.

• 3 years ago

Will a win by checkmate increase my rating more than a win because my opponent runs out of time?

• 3 years ago

That's impossible.

• 3 years ago

I won a game and lost 300 elo is this a bug?

• 3 years ago

One problem with the rating system is this: I often sit in the evening playing online chess in the bar drinking beer. At the beginning of the evening I will probably be playing close to my best. By the end of the evening I will be making the most elementary blunders!

• 3 years ago

What is the calculation at the begining which came to 150?

• 3 years ago

I just read the glicko system article and can see why it would be difficult to do by hand!

• 3 years ago

I don't understand any rating system and I don't want to.  I just want to know that there is one and that everyone I am playing is on the same rating system.  I wish this site used a system that was more used world wide, but it sounds like this one may end up being one that is.  I haven't played very many games here, but my rating is around what it was on another site where I played many games.  In a nutshell, if you beat someone that sucks its not as big a win as it you beat someone good, and vice verse with losses.  Having the same number of points for a winning game is rather stupid, since beating someone better should be worth more than beating a lesser player.  After all, you don't get the same sense of accomplishment when you beat a 3 year old in a foot race (assuming your at least a teenager or adult) versus beating a current Olympic Gold Medalist Sprinter.  If you do you are quite sad.  ENJOY CHESS!

• 3 years ago

@ krunalgohil19 okay..i will try that..cheers ! :)

• 3 years ago

@nen:go to live chess

• 3 years ago
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• 3 years ago

Thanks CharlesRoberson , I just checked rated and unrated games, most were unrated, so I know now why my rating was not moving.

Thanks a lot for the answer.

• 3 years ago

black-horseltu,

sounds like you play some rated games and some unrated games. check the details in your game archive: home->game archive.

• 3 years ago

My rating is not moving. Currently I won few games and lost one. Apparently loss was counted and wins no!!! What is going on?

• 3 years ago

What you mean jajr??

• 3 years ago

why my rating don"tmove?

• 3 years ago

@jhorlock:yeah......i understand......thanks......