OneTaskBy Tim King · Updated
Swiss Pairing Generator
Pair Swiss-System Rounds by Score With No Rematches and Buchholz Tiebreaks
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How the Swiss Pairing Generator works
This Swiss pairing generator runs a Swiss-system tournament round by round. List the players with optional ratings, pair round 1, enter the results, then pair the next round. Players meet others on the same score, never face the same opponent twice, get balanced colours, and the standings rank everyone with Buchholz and Sonneborn-Berger tiebreaks.
A Swiss system lets a large field play a handful of rounds and still produce a fair winner. Nobody is knocked out, and because winners keep meeting winners, the leaders sort themselves out far faster than a round robin would. It is the standard format for chess, and common in card games, esports, debating and board game clubs.
How the Swiss pairing generator makes pairings
Round 1 sorts players by rating and pairs the top half against the bottom half, so the first seed meets the player just below the middle. From round 2 on, players are sorted by points, then tiebreaks. Each player is paired inside their score group, top half against bottom half, and dropped to the next group only when that is the only way to avoid a rematch. With an odd number of players, the lowest-ranked player who has not had a bye sits out for one point. Colours go to whoever has had fewer whites, then whoever had black last round.
First example. Eight players, three rounds. After round 1 four players are on 1 point and four on 0. Round 2 pairs the 1-pointers against each other and the 0-pointers against each other, so after round 2 exactly two players are on 2 points. Round 3 puts them together to decide the winner.
Second example. Nine players. The ninth seed gets the round 1 bye and a free point. In later rounds the bye moves to the lowest-ranked player who has not had one, so nobody sits out twice until everyone has.
Rounds needed for a clear winner, one point per win
| Players | Minimum rounds | Common choice |
|---|---|---|
| 4 | 2 | 3 |
| 6 | 3 | 3 |
| 8 | 3 | 3 or 4 |
| 10 | 4 | 4 |
| 12 | 4 | 4 or 5 |
| 16 | 4 | 5 |
| 20 | 5 | 5 |
| 24 | 5 | 5 or 6 |
| 28 | 5 | 6 |
| 32 | 5 | 6 |
| 40 | 6 | 6 |
| 48 | 6 | 6 or 7 |
| 56 | 6 | 7 |
| 64 | 6 | 7 |
| 80 | 7 | 7 |
| 96 | 7 | 7 or 8 |
| 112 | 7 | 8 |
| 128 | 7 | 8 |
| 160 | 8 | 8 |
| 200 | 8 | 9 |
| 256 | 8 | 9 |
| 300 | 9 | 9 |
| 400 | 9 | 10 |
| 512 | 9 | 11 |
Tips and pitfalls
- Ratings are optional. Put a number after a name, like "Alice 1850", to seed round 1. Players with no rating are seeded below rated players in the order you listed them.
- Enter every result before pairing the next round. The button stays disabled until the current round is complete, because each pairing depends on the scores.
- Use Undo last round to fix a mistake. Pairings for later rounds are rebuilt from scratch, so correcting an old result never leaves the draw inconsistent.
- Small fields run out of fresh opponents. With six players and five rounds it becomes a round robin. If no pairing without a rematch exists, the generator allows one rather than failing.
FAQ
What is a Swiss-system tournament?
It is a format where every player plays every round, and each round pairs players with similar scores who have not met before. After a set number of rounds the highest score wins. It finds a winner in far fewer rounds than a round robin and without the early exits of a knockout.
How many rounds should a Swiss tournament have?
At least the base-2 logarithm of the player count, rounded up, so 3 rounds for 8 players, 5 for 32 and 7 for 128. That is the minimum for one player to finish with a perfect score alone. Most organisers add one or two rounds so the places below first are better separated.
What is Buchholz?
Buchholz is the sum of the final scores of every opponent you played. A player whose opponents scored well had a harder tournament, so when two players finish on the same points, the one with the higher Buchholz ranks first. A bye adds nothing to it.
What is Sonneborn-Berger?
Sonneborn-Berger adds the full score of every opponent you beat and half the score of every opponent you drew with. It rewards beating strong players rather than weak ones, and is the second tiebreak here, used when points and Buchholz are both level.
Is this the same as official FIDE Dutch pairing?
It follows the same main principles, pairing within score groups top half against bottom half with no rematches and balanced colours, but it is not a certified FIDE pairing engine. For rated events that need official pairings, use approved software. For clubs, schools and casual events it works well.
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