Spartanburg Chess Club Rating System
Our Club rating system has a theoretical mean (average) of 500. The current mean is *503.3 with a standard deviation of 41.0. A standard deviation is a measure of how scores vary from one another. Approximately, 68% of players score within plus or minus one standard deviation of the mean, in this case, 462.3 to 544.3. Our system takes into account multiple factors including: rating difference between a player and his or her opponents, color played, time control, and modification due to special events.
In a nutshell, this is how ratings are calculated:
1) Multiply a players rating times the number of games played in the event. (New players start with a rating of 500.)
2) Sum the opponents' ratings.
3) Subtract step 2 from step 1.
4) Multiply step 3 by .05. If the result is a positive number, subtract from the player's rating. If it is a negative number, add to the player's rating.
5) Add 8 points for each win with White, 12 points for each win with Black, and 5 points for each draw with Black.
6) Subtract 12 points for each loss with White, 8 points for each loss with Black, and 5 points for each draw with White.
7) For tournaments with a time control of Game/30 or slower, you can stop with step 6. If the time control is faster than G/30 (such as blitz games), the point values in steps 4 through 6 are halved.
For special events, for example, Crazy-It, final scores are tallied and the median score is assigned zero change in rating. Each position above the median gains 1/2 point per position added to the player's rating. Conversely, each position below the median results in a 1/2 point loss per position to a player's rating. (Note: Not all special events are subject to this rating adjustment.)
*The reason for "rating drift" is partly due to rounding of scores, partly due to some trial-and-error with the rating system, partly due to new players added to the system while some players drop out, and partly due to math errors when calculating these ratings by hand.