Sonneborn-Berger

Sonneborn-Berger (SB) gives more weight to points earned against opponents who finish with high scores. For each round, the opponent's final score is multiplied by the points scored against that opponent, and all those products are added.

With the usual scoring of 1 point for a win, half a point for a draw, and 0 for a loss, the effect is easy to read: a win contributes the opponent's full final score, a draw contributes half, and a loss contributes 0. If an opponent finishes with 6 points, a win against that opponent contributes 6 to SB, a draw 3, and a loss 0.

This differs from Buchholz, where the same 6-point opponent contributes 6 regardless of the game result. Sonneborn-Berger can therefore reflect against whom a player earned their points. In Swiss events, the International Chess Federation (FIDE) applies specific rules so unplayed rounds are handled in a defined way.