A Swiss tournament is for a club night or a weekend event with more players than there is time for a round robin. Nobody is knocked out, everyone plays every round, and each round pairs people who are doing about equally well. Chess clubs, darts leagues, board-game and card-game events use it.
Open the free pairing tool (it is the Swiss card on the page; pair each round by pasting in the results so far)
Six invented players, seeded in the order they signed up. Six players need 3 rounds. Round 1 has no scores yet, so the seed order decides: the top half plays the bottom half.
| Round 1 | White | Black |
|---|---|---|
| Board 1 | Ana | Dee |
| Board 2 | Ben | Eli |
| Board 3 | Cy | Fay |
Suppose Ana, Ben and Fay win. The three winners now have 1 point and the three losers 0, so round 2 pairs winners with winners and losers with losers, with nobody meeting a previous opponent:
| Round 2 | White | Black |
|---|---|---|
| Board 1 | Ana | Ben |
| Board 2 | Fay | Dee |
| Board 3 | Eli | Cy |
Fay, on 1 point, plays Dee, on 0, because the other two 1-point players already meet each other: the tool shows that as a "floater" and says so rather than hiding it. Colours alternate, so nobody is white three times running. The pairing is checked by a separate validator before it is shown.
Enough that one player can be clearly ahead: the next whole number above log base 2 of the player count. Six or eight players need 3 rounds, sixteen need 4. More rounds sort the middle of the table more finely, but the top places are usually settled by this number.
Everyone is sorted by score, then players with the same score are paired top half against bottom half, so the strongest of a group meets the weakest of that group. Nobody plays the same opponent twice. In round 1 nobody has a score yet, so the seed order decides.
One player gets a bye each round and is scored as a win. The bye goes to the lowest-ranked player who has not had one yet, so nobody gets two byes before everyone has had one.
By Buchholz: the sum of your opponents' scores. Beating players who went on to do well is worth more than beating players who lost everything. Still level? Sonneborn-Berger is next: the full score of each opponent you beat plus half the score of each you drew, so a win over the leader outweighs a win over the player who lost everything. Players still level after that keep their seed order.
Related: how to make a round-robin schedule for small leagues where everyone can play everyone.