Chess.com uses the Glicko-2 rating system for 4 Player Chess (4PC), similar to regular chess. However, because you’re playing against multiple opponents instead of just one, the rating calculations work a bit differently.
Free For All
In Free For All mode, your rating is adjusted based on the average rating of your three opponents.
For example, if the players in a game have ratings of 1500, 1600, 1700, and 1800, the 1500-rated player’s rating change would be calculated as if they were playing against a 1700-rated opponent (the average of 1600, 1700, and 1800). Meanwhile, the 1800-rated player’s rating change would be calculated as if they were playing against a 1600-rated opponent (the average of 1500, 1600, and 1700).
The rating adjustment also varies depending on your placement in the game:
1st place: Your rating is adjusted as if you won three games against the calculated rating.
2nd place: Your rating is adjusted as if you won two games and lost one game against the calculated rating.
3rd place: Your rating is adjusted as if you won one game and lost two games against the calculated rating.
4th place: Your rating is adjusted as if you lost three games.
Teams
In Teams mode, the rating adjustment is calculated similarly to a 1v1 game, but with a slight difference in how team ratings are determined — Instead of simply averaging the ratings of the two team members, the team rating is weighted toward the higher-rated player.
The formula used is:
(2H+1L)/3
Where H is the higher rating and L is the lower rating.
For example, if Team A consists of players rated 1800 and 1300, and Team B consists of players rated 1500 and 1600, the rating adjustment would be calculated as if a 1633-rated player (Team A) played against a 1566-rated player (Team B).