For each match an "expected" score is calculated from the rating difference of the two players (if the ratings are equal, the expected score is 0.5).

This expected score is then compared to the actual score of the game (1 for win, 0 for loss, or can be anything in-between for multiple ends).

If the expected score for the player was higher than the real score, the rating drops, if the score is higher than the expected score, the rating is raised.

Check the rating calculator for details.

Formulae:
 
Where E is the expected score, and dr is the difference in ratings before the match. 

The rating change is calculated from the following:
 
Where W is the score of the event, We is the expected score, n is the sum of the scores by both players. 


The system is based on the rating system developed by Prof. Árpád Élő.