Tournament bracket maker

How to use the bracket maker

1. List the entrants, one per line. In Seeded mode put the strongest first: line 1 is seed 1, line 2 is seed 2, and so on.
2. Pick Random instead if you want an open draw, for example at a pub darts night or a five-a-side cup where nobody is ranked.
3. Press Make bracket. The tool works out the bracket size, places the byes and shows every round up to the final.
4. After each match, click the winner's name. They move into the next round. Click again to undo.
5. Print the bracket for the wall, or copy it as text to share in a group chat. Your bracket is saved in this browser, so you can close the page and carry on later.

How the seeding works

This tournament bracket maker uses standard seeding: seed 1 plays the lowest seed, seed 2 plays the second lowest, and the two halves of the draw are arranged so that seeds 1 and 2 can only meet in the final, seeds 1 to 4 only from the semi-finals, and so on. In an 8-team bracket the first-round matches are 1 v 8, 4 v 5, 2 v 7 and 3 v 6. Tennis, snooker and most cup competitions with seeds use this pattern.

When the number of entrants is not a power of two, the empty slots become byes. Byes always sit opposite the top seeds, so a bye never meets another bye and every second-round match is between two real entrants.

Worked example: 10 teams

Ten teams need a 16-slot bracket, so there are 6 byes. Seeds 1 to 6 go straight through to round two. Seeds 7 to 10 play two first-round matches: 7 v 10 and 8 v 9. From then on it is a normal knockout: 8 teams in the quarter-finals, 4 in the semi-finals, then the final. In total 9 matches are played over 4 rounds.

Tips for a smooth knockout

• Too many byes? With 17 entrants you get 15 byes, which feels odd. Consider a short qualifying round, or a group stage with the fixture generator before the knockout.
• Seeding without rankings: use last year's results, a league table, or a quick group stage. If there is nothing fair to go on, choose Random.
• Running on time: count the matches in each round and divide by the number of pitches, boards or tables to see how long each round will take.
• Need random teams first? Split a group of players into fair sides with the random team generator, then put the teams in the bracket.

How we tested it

We ran the bracket code for 2, 3, 5, 6, 8, 10, 13, 16, 17, 31, 64, 100 and 128 entrants. For each size we checked the bracket size, that the number of byes equals bracket size minus entrants, that byes only go to the top seeds and never face each other, that playing the whole draw with the higher seed always winning makes seed 1 champion, that exactly entrants − 1 matches are played, and that the round count is right. We also checked that changing an early result clears the later result that depended on it.