Swiss pairing generator

How pairing works

Round 1 pairs seed 1 against the middle of the field, seed 2 against the next, and so on. After each round, players with the same score meet, nobody repeats an opponent, and in an odd field the bye goes to the lowest-ranked player who has not had one.

Enter a win, loss or draw for each game. The standings rank by points, then Buchholz, the total score of your opponents.

Colours

The pairings do not assign colours (white and black in chess). Set colours by hand when you post each round.

A worked round

Take 16 players. Round 1 pairs 1 v 9, 2 v 10 and so on down to 8 v 16. Say the higher seeds all win. Eight players now have 1 point and eight have 0. Round 2 pairs inside each score group: 1 v 5, 2 v 6, 3 v 7 and 4 v 8 among the winners; 9 v 13, 10 v 14, 11 v 15 and 12 v 16 among the losers. Nobody meets anyone twice.

By round 4 the field has split into score groups of different sizes, and the games that matter most are the ones between players on the same score. That is why Swiss finds a clear winner in about log2 of the field rounds.

What to post for the players

Post each round as a table of board numbers, with the two names and the colours if your game uses them. Set a time limit, and ask players to report the result at the table before the next round is paired. If a player drops out, remove them before pairing; the generator treats the empty seat as a bye for the opponent.

Questions