The Sonneborn–Berger score is a tiebreak criterion for round-robin tournaments, where everyone plays everyone. It shows against whom a player scored their points: wins over strong opponents count for more than wins over weak ones.
How to calculate it
A player's Sonneborn–Berger score equals:
- the sum of the points of all opponents they beat,
- plus half the points of the opponents they drew with.
Losses add nothing.
Example
A four-player tournament, each player has played three games:
| A | B | C | D | Points | |
|---|---|---|---|---|---|
| A | — | ½ | 1 | ½ | 2 |
| B | ½ | — | ½ | 1 | 2 |
| C | 0 | ½ | — | 1 | 1½ |
| D | ½ | 0 | 0 | — | ½ |
A and B have 2 points each. Let us calculate their scores:
- A beat C (1½ points) and drew with B (half of 2 = 1) and D (half of ½ = ¼). Total: 1½ + 1 + ¼ = 2¾.
- B beat D (½ point) and drew with A (half of 2 = 1) and C (half of 1½ = ¾). Total: ½ + 1 + ¾ = 2¼.
First place goes to A: their win was against a stronger opponent.
When it is used
The Sonneborn–Berger score is used in round-robin tournaments, usually after the direct encounter. The order of tiebreak criteria is set in advance in the tournament regulations. For Swiss-system tournaments the Buchholz score is more suitable.
Other ways of deciding places are covered in the article “Tiebreak”.