Round robin calculator

Teams × (teams − 1) ÷ 2. Each team plays every other team once, and each match involves two teams, so 8 teams play 8 × 7 ÷ 2 = 28 matches.

With an even number of teams, teams − 1 rounds and nobody sits out. With an odd number, as many rounds as teams, and one team sits out each round, so every team sits out exactly once.

28 matches over 7 rounds, with 4 matches each round. On 2 courts that's 14 time slots; at 15 minutes a match, about 3.5 hours of play.

21 matches over 7 rounds. Each round has 3 matches and one team sits out, so you need 3 courts to play a round at once.

10 teams: 45 matches over 9 rounds. 12 teams: 66 matches over 11 rounds. 16 teams: 120 matches over 15 rounds. The table below has every size from 3 to 32.

Twice as many: teams × (teams − 1). Everyone plays everyone twice, usually once at home and once away.

Teams − 1, because every match knocks out exactly one team and everyone but the winner is knocked out once. 12 teams play 11 matches over 4 rounds, with 4 byes in round 1 so that round 2 has 8 teams. Add one for a 3rd-place playoff.

2 × teams − 2, or 2 × teams − 1 if the grand final has to be played twice. Every team except the champion loses twice, and the champion loses once at most.

Divide the matches into time slots on your courts, then multiply by the length of a match. The calculator does this with the same scheduler as the free round robin generator, so the slots match the schedule it prints. Add time for changeovers and breaks.