Ratings System Explanation

The purpose of the following table is for calculating rating changes and performance ratings. On the left side, there are percentages, which indicate how often you should win the game, if the player is rated that many points above you. Since absolute values are simply reversed when going the in the opposite direction of percentages, those over 50% are omitted. For example, you are expected to beat somebody 117 points above you 34% of the time.

The right side is for Performance Rating (PR) calculations. An example here would be if you win 7 games in an 11 round tournament, your PR will be 99 points higher than the average of your opponents' ratings. To save space, PR's equal the field played against if exactly half of the games are won. Additionally, perfect records yield performance ratings 700 points above the field played.

Thanks to John Chew and Steven Alexander for most of this information.




WIN  RATG  WIN  RATG                       PERFORMANCE RATINGS
EXP  DIFF  EXP  DIFF  15-1=434 14-2=326 13-3=251 12-4=191 11-5=139 10-6=91  9-7=45
 1%  655   26%  182   14-1=425 13-2=315 12-3=239 11-4=177 10-5=122  9-6=72  8-7=24
 2%  580   27%  173   13-1=415 12-2=302 11-3=224 10-4=161  9-5=104  8-6=51
 3%  532   28%  164   12-1=404 11-2=289 10-3=209  9-4=143  8-5= 83  7-6=28
 4%  495   29%  156   11-1=392 10-2=274  9-3=191  8-4=122  7-5= 60
 5%  465   30%  148   10-1=378  9-2=257  8-3=172  7-4= 99  6-5= 33
 6%  440   31%  140    9-1=362  8-2=239  7-3=148  6-4= 72
 7%  418   32%  132    8-1=346  7-2=217  6-3=122  5-4= 40
 8%  397   33%  125    7-1=326  6-2=191  5-3= 91
 9%  379   34%  117    6-1=302  5-2=161  4-3= 51
10%  362   35%  109    5-1=274  4-2=122
11%  347   36%  102    4-1=239  3-2= 72
12%  332   37%   94    3-1=191
13%  318   38%   87
14%  305   39%   79
15%  293   40%   72
16%  281   41%   64
17%  270   42%   57
18%  259   43%   50
19%  249   44%   43
20%  239   45%   36
21%  229   46%   29
22%  219   47%   21
23%  209   48%   14
24%  200   49%    7
25%  191   50%    0
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