Harkness Rating System

For simplicity, OCC uses the Harkness Rating System. All games; Ladder, Round-Robin, Swiss, Knockout, or Tournament will use this system.

HARKNESS SYSTEM*

Opponent Rating Difference If High Wins Add to Winner and Deduct from Loser If Low Wins Add to Winner and Deduct from Loser If a Draw Add to Low Deduct High
0 to 24 16 16 0
25 to 49 15 17 1
50 to 74 14 18 2
75 to 99 13 19 3
100 to 124 12 20 4
125 to 149 11 21 5
150 to 174 10 22 6
175 to 199 9 23 7
200 to 224 8 24 8
225 to 249 7 25 9
250 to 274 6 26 10
275 to 299 5 27 11
300 or more 4 28 12

*Official Chess Handbook, p. 156

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