Ratings on Chess.com

Every player on Chess.com has a rating designed to measure their skill level and match them against opponents of similar ability.

You may have noticed that your rating doesn’t always change by the same amount after a win or loss. What causes this variation?

A few factors can affect how much your rating changes after you play a game. These factors include:

1. The difference in rating between you and your opponent.

2. How confident we are of your rating.

3. How confident we are of your opponent’s rating.

    

Rating change factors

Number one is straightforward: the greater the rating disparity between you and your opponent, the larger the potential rating change. Winning against a higher-rated opponent results in a bigger increase, while losing to a lower-rated opponent results in a bigger decrease.

Numbers two and three are more complex but crucial. Confidence in the ratings is a significant reason for substantial changes in your rating after a game.

Glicko system

Chess.com uses the Glicko rating system, which includes a measure called ‘rating deviation’ (RD) to indicate our confidence in your rating. If you’re new and haven't played any games, the system is unsure of your 'real' rating, so your rating will fluctuate significantly during your first few games.

If you haven't played in a while, your RD will increase, causing your rating to change more dramatically after your next game. This happens because we can't determine whether you've been practicing elsewhere or haven't played at all.

The same applies to your opponents. If you lose to someone with a much lower rating but a high RD (they haven’t played in a long time), your rating won’t change much since their rating may not be accurate.