Chess Ratings - How They Work

  • erik
  • | Aug 23, 2007

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!)

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.

The Glicko System (used by, the Australian Chess Federation, and some other online sites) is a more modern approach that builds on some of the concepts above, but uses a more complicated formula. (This only makes sense now that we have computers that can calculate this stuff in the blink of an eye - when Elo created his system they were doing it on paper!) It is a bit trickier than the Elo system, so pay attention. With the Elo system you have to assume that everyone's rating is just as sure as everyone else's rating. So my rating is as accurate as your rating. But that is just not true. For example, if this is your first game on and you start at 1200, how do we really know what your rating is? We don't. But if I have played 1,000 games on this site, you would be much more sure that my current rating is accurate. So the Glicko system gives everyone not only a rating, but an "RD", called a Rating Deviation. Basically what that number means is "I AM 95% SURE YOUR RATING IS BETWEEN X and Y." (Nerd Fact: In technical terms this is called a "confidence interval".) If this if your first game on I might say, "I am 95% sure that your rating is somewhere between 400 and 2400". Well that is a REALLY big range! And that is represented by a really big RD, or Rating Deviation. If you have played 1,000 games and your rating is currently 1600 I might say "I am 95% sure your rating is between 1550 and 1650". So you would have a low RD. As you play more games, your RD gets lower. To add one extra wrinkle in there, the more recent your games, the lower your RD. Your RD gets bigger over time (because maybe you have gotten better or worse over time - I'm just less sure of what your actual rating is if I haven't seen you play recently). Now, how does this affect ratings? Well, if you have a big RD, then your rating can move up and down more drastically because your rating is less accurate. But if you have a small RD then your rating will move up and down more slowly because your rating is more accurate. The opposite is true for your opponent! If they have a HIGH RD, then your rating will change LESS when you win or lose because their rating is less accurate. But if they have a LOW RD, then your rating will move MORE because their rating is more accurate.

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):

- The Glicko System by Professor Mark Glickman, Boston University

- Introduction to Chess Ratings (Elo mostly) on


  • 5 years ago


  • 5 years ago



    Have been challenged to a tournament. Haven't "archived" it so lost in some Martian orbit.

    How do I :

    a) contact player (named MarijaSM) controlling tourney?

    b) How are these tournaments controlled? Do I play x players in a set time (eg: 3 months)?

    c) How do I find previous message/challenge sent to me?

    Am so enjoying the games.

    Thank you, e~

  • 5 years ago


    I have a question,

       Will timeout affect the rating?

  • 5 years ago


    why some people doesn't dropped there rating while they resign. While I did same and lost my rating

  • 5 years ago


    I noticed something rather strange, and am wondering whether this is expected in the Glicko rating system. Consider these three consecutive turn-based games, dated just a couple days apart:

    Turn-Based Game  RonnieBurton(1359)  reesmf (750) 1-0 (won) 10 days 20 5/27/2008 view  
    Turn-Based Game  reesmf (783)  RonnieBurton(1326) 0-1 (won) 10 days 31 5/23/2008 view  
    Turn-Based Game  RonnieBurton(1326)  reesmf (783) 1-0 (won) 10 days 34 5/18/2008 view  

    None of these are marked as unrated, so presumably they were rated. How is it possible that the win on 5/23 results in no change in the players' ratings, and the one on 5/27 does?

    Another puzzling occurrence:

    Turn-Based Game  NatalieKleffman(1316)  reesmf (1284) 0-1 (won) 10 days 21 6/05/2008 view  
    Turn-Based Game  RonnieBurton (1359)  reesmf (750) 1-0 (lost) 10 days 20 5/27/2008 view  

    Looking at the past history of the Black, you can see that his win was preceded by 21 losses (all to the player that was rated 1326 most of the time), 1 draw (same player), and one win against a 768-rated player. None of the games are tagged as unrated.

    Now a single win produces rating gain of 534 points.

    Is such a gain normal and expected in the Glicko system?

    Just curious.

  • 5 years ago


    i agree with mr. ozfamilyman.. i am playing 100s of games in my vacation and keep me away at times.. i dont win many games, but i am happy to play with everyone who come across, without checking their rating.. some people abort games when they see someone with lower rates, coz, may b they r afraid of losing to them which may result in heavy drop in ratings.. such people kill the spirit of game. if they r not confident enaf to play with everyone, or r afraid of losing ratings and feels gud at living with these high points gained thru filtering, they r unaware of the original spirit of life...

  • 5 years ago


    Cool  Hi mrkoolarana of USA !! I see you joined with in July last  and was wondering how & with whom to play with  and fit in !! I saw your query to-day !! May be its a bit late and by this time you got your self fit in and found mates to play with chess !!! and enjoying. Needless to say again that it was very easy to fit in with the game set up by selecting your option from the games menue which is instantly presented  when logged in. If you are still in problem ,please ventilate here or in Forum for general discussion.

  • 5 years ago


    ssdeep: "i am new to the online chess  turn based chess in this site,so far i won 7 games on a trot albeit with lower rated players,for the first six games my rating peaked to 1622 then even after winning the 7th on it suddenly dropped to 1422?!,and the 7th game was won against a 1300+ player,most of the games i played wer part of some tournament where i cannot decide who my opponent is."

    Hey ssdeep, your 7th game was a chess960, it have a seperate rating, so it did increase to 1422. 

  • 5 years ago


    Hi  dear Lorraine219,Manchester UK. You can do it at the begining. Before you start the game you click on the game options menu selecting "Rated". Thats all!!

  • 5 years ago



  • 5 years ago


    Innocent Just click on the opponents name , it will appear !!

  • 5 years ago


    i am new to the online chess  turn based chess in this site,so far i won 7 games on a trot albeit with lower rated players,for the first six games my rating peaked to 1622 then even after winning the 7th on it suddenly dropped to 1422?!,and the 7th game was won against a 1300+ player,most of the games i played wer part of some tournament where i cannot decide who my opponent is.

  • 5 years ago


    I've noticed several "unsportsmanlike" players in They will either let the game time out, in an effort to not "lose" or will disconnect....which I guess, to them, is preferable to suffering a "loss".

    What bothers me is how some of my opponents have a rather high rating, but after I've won, their rating drops drastically. For instance, today, I won a game against an individual with a rating over 1200. After the game was finished, his/her rating dropped 170 points. I only gained 9 points. Just curious how that happens.

  • 5 years ago


  • 5 years ago


    Being check mated would mean lowering your rating !!  Reading the article on how chess Rating works' is advisable here!!

  • 5 years ago


    Rating points gained or lost are based on your rating at the beginning of the game.

    If you click on a member's name, look at their Online Chess profile or Live Chess profile and you can see their rating.

  • 5 years ago


    How can I see the rating of another member?

  • 5 years ago


    Does the rating adjustment depend on your rating and your opponent's rating at the start of the game?  Or at the end of the game?

  • 5 years ago


    SmileRoy777 has expounded a theory & formula based on income (personal?) vis-a-vis identifying environmental element methodology ! I think this is not based on the Law of Uniformity to be adhered in Chess.I  would be sorry, if this hurts my friend in chess.

  • 5 years ago


    Innocent I think our friend  Roy777,gin gin. Australia is on a bigger research on the subject since two months back. i dont know where is his stand now!! But I agree with you in so far as that  " no move no points" win.

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