How Ratings Work on Chess.com
Everyone on Chess.com has a rating. The purpose of this rating is to try to measure the level of skill of each player, to better match you against other players of equal skill.
You’ve probably noticed that after you win or lose a game, your rating doesn’t always go up or down by the same amount. What causes this difference?
A few things can affect how much your rating changes after you play a game. Some things that can affect this are:
The difference in rating between you and your opponent
How confident we are of your rating
How confident we are of your opponent’s rating
Number one is pretty straight forward. If you win against someone who has a much higher rating than you, your rating will go up by a higher amount than if you win against someone of your same rating, or of a lower rating.
Similarly, if you lose against someone with a lower rating, your rating will go down more than if you lost to someone with a higher rating.
Numbers two and three on the list are a bit more complicated. It might sound strange, but confidence in the rating is the main reason for big changes in your rating after a game.
Chess.com uses the Glicko rating system, and part of this system is a number called a ‘rating deviation’ or RD, which measures how sure we are of what your rating is. If you've never played any games on Chess.com before, the system has no idea of what your 'real' rating is, so it will move your rating up and down a lot during the first few games you play.
If you aren't new, but haven't played any games for a while, your RD will also go up, and the next game you play might change your rating by a lot.
This is because Chess.com hasn’t seen any games from you in a while, and there is no way to tell whether you’ve been practicing and getting better other places, or if you haven’t been playing at all.
The same applies to your opponents as well. If you lose to someone who is several hundred rating points lower than you, but with a very high RD (they haven't played in a long time), your rating won’t change much, because we can’t be sure that their rating is accurate.
If you’re curious about more of the inner workings of the rating system, check the articles here and here!
Our advice to you, though, is to just play games and have fun, and let the rating sort itself out!