The formulas
- Single elimination: n − 1 games.
- Double elimination: 2n − 2 games, plus 1 if the grand final is replayed.
- Round robin: n × (n − 1) ÷ 2 games.
- Double round robin: n × (n − 1) games.
- Swiss: ⌊n ÷ 2⌋ × rounds games.
Why they are what they are
Elimination formats are about losses: a game produces exactly one loss, and everyone but the champion has to take one (single) or two (double). Round robins are about pairings: each of the n teams plays n − 1 others, and each game counts for two teams.
From games to time
Time on court is games × minutes per game. Clock time is shorter if games run at once. A round has at most ⌊n ÷ 2⌋ games, so you cannot use more courts than that in the first round.
Worked examples
Twelve teams in single elimination play 11 games. In double elimination they play 22, or 23 with a replay. A round robin of twelve takes 66 games, and Swiss with twelve players and four rounds takes 24.
Questions
Does a bye count as a game?
No. A bye is a slot with no opponent, not a game.
How many rounds does a Swiss tournament need?
The base-2 logarithm of the player count rounded up, and never fewer than three. Twelve players play four rounds.