The Sonneborn-Berger system is used in tournament's tie-breaks when two or more players have the same highest score.
The player with the highest score and most Sonneborn-Berger points will be the winner.
When there are more then one winner, all of them can be declared as winners or an extra round will be played to determine a winner.
Note: Sonneborn-Berger points calculation is applicable only for players with the same highest score in the group.
In this system, for each player with the same highest score the sum of defeated and draw opponents' points will be calculated.
To help you better understand this system please see explanation below.
Here are the steps that need to be performed in order to calculate points in Sonneborn-Berger system:
1. Find players with the same highest score.
Note: If there is only one player, this player will be the winner and there is no need for Sonneborn-Berger point calculation.
2. For each player with the highest score create a list of opponents who was defeated.
3. For each player with the highest score calculate sum of scores for each defeated opponent.
In following examples show how Sonneborn-Berger points get calculated. The winner is determined only between players with the same maximum number of points. The tournament in examples has double round-robin system with 4 players.
Example 1:
| A | B | C | D | score | defeated opponent | Sonneborn-Berger points | Comments | ||
| A | 0:1 | 1:1 | 1:0 | 4 | B C C D | 4+3+3+1 = | 11 | Winner | |
| B | 1:0 | 0:1 | 1:1 | 4 | A C D D | 4+3+1+1= | 9 | ||
| C | 0:0 | 1:0 | 1:1 | 3 | B D D | 4+1+1= | 6 | Sonneborn-Berger points are irrelevant | |
| D | 0:1 | 0:0 | 0:0 | 1 | A | 4 | 4 | Sonneborn-Berger points are irrelevant | |
Example 2:
| A | B | C | D | score | defeated opponent | Sonneborn-Berger points | Comments | ||
| A | 1:1 | 1:1 | 0:0 | 4 | B B C C | 4+4+0+0 = | 8 | Winner | |
| B | 0:0 | 1:1 | 1:1 | 4 | C C D D | 0+0+4+4= | 8 | Winner | |
| C | 0:0 | 0:0 | 0:0 | 0 | 0 | Sonneborn-Berger points are irrelevant | |||
| D | 1:1 | 0:0 | 1:1 | 4 | A A C C | 4+4+0+0= | 8 | Winner | |
Example 3:
| A | B | C | D | score | defeated/draw opponent | Sonneborn-Berger points | Comments | ||
| A | 1:1/2 | 1:1 | 0:0 | 3.5 | B B C C | 3.5+3.5+1.5+1.5 = | 10 | ||
| B | 0:1/2 | 1:1 | 1:0 | 3.5 | A C C D | 3.5+1.5+1.5+3.5= | 10 | ||
| C | 0:0 | 0:0 | 1/2:1 | 1.5 | D D | 0 | Sonneborn-Berger points are irrelevant | ||
| D | 1:1 | 0:1 | 1/2:0 | 3.5 | A A B C | 3.5+3.5+3.5 +1.5= | 12 | Winner | |