Swiss tournament generator

The next round draws itself

Only round one is written up front, because the rest of them are not knowable yet. When the last result of a round goes in, the next round is paired from the table as it stood at that moment — and never from the round being drawn, which is the mistake that produces a pairing depending on its own result.

There is nothing to press. Finishing a round is what draws the next one. There is a manual pairing endpoint, but it is the repair path rather than the normal one.

How many rounds

The default is ceil(log2(teams)) — the fewest rounds that can still leave exactly one team unbeaten — with a floor of three and a ceiling of however many opponents there actually are. Sixteen teams is four rounds; thirty-two is five; sixty-four is six.

You can set it higher for a longer day. Run it long enough against a small field and the draw will run out of fresh opponents and start repeating a meeting; nothing is wrong when that happens, but you are told about it rather than left to notice.

Byes score

An odd field means one team sits out each round, and in a Swiss that bye takes the points for a win. Scoring it zero would send whoever happened to be the odd one out to the bottom of the table for something they had no part in.

Correcting a result redraws what it fed

Fix a score and the round it fed is redrawn — but only while nothing from that round onwards has been played. Matches cannot be unplayed to match a corrected table, so past that point the correction updates the standings and leaves the pairings alone.

Common questions