Round robin formula: games, rounds and time
Every round robin is described by three numbers: how many games, how many rounds, and how many games each team plays. All three come from one idea — every pair of teams meets once.
The formula
With n teams:
- Games = n × (n − 1) ÷ 2
- Games per team = n − 1
- Rounds = n − 1 if n is even, or n if n is odd
- Games per round = n ÷ 2, rounded down
Why n × (n − 1) ÷ 2? Each of the n teams plays n − 1 opponents, which counts n × (n − 1) “appearances”. But every game has two teams in it, so each game was counted twice. Divide by 2.
For 7 teams: 7 × 6 ÷ 2 = 21 games.
Odd numbers need an extra round because one team always lacks an opponent. With 7 teams, only 3 games fit in a round (6 teams playing, 1 resting), so 21 games take 7 rounds. That resting slot is the bye.
Table: 3 to 20 teams
| Teams | Games | Rounds | Games / team | Games / round | Double RR |
|---|---|---|---|---|---|
| 3 | 3 | 3 | 2 | 1 | 6 |
| 4 | 6 | 3 | 3 | 2 | 12 |
| 5 | 10 | 5 | 4 | 2 | 20 |
| 6 | 15 | 5 | 5 | 3 | 30 |
| 7 | 21 | 7 | 6 | 3 | 42 |
| 8 | 28 | 7 | 7 | 4 | 56 |
| 9 | 36 | 9 | 8 | 4 | 72 |
| 10 | 45 | 9 | 9 | 5 | 90 |
| 11 | 55 | 11 | 10 | 5 | 110 |
| 12 | 66 | 11 | 11 | 6 | 132 |
| 13 | 78 | 13 | 12 | 6 | 156 |
| 14 | 91 | 13 | 13 | 7 | 182 |
| 15 | 105 | 15 | 14 | 7 | 210 |
| 16 | 120 | 15 | 15 | 8 | 240 |
| 17 | 136 | 17 | 16 | 8 | 272 |
| 18 | 153 | 17 | 17 | 9 | 306 |
| 19 | 171 | 19 | 18 | 9 | 342 |
| 20 | 190 | 19 | 19 | 10 | 380 |
Notice how fast it grows: doubling from 8 to 16 teams more than quadruples the games, from 28 to 120. That’s why big fields usually switch to pools or Swiss.
How long will it take?
A quick estimate of playing time:
Time ≈ games × (game length + changeover) ÷ courts
Example: 10 teams, 20-minute games, 5 minutes to change over, 3 courts.
45 games × 25 minutes = 1,125 court-minutes. Divided by 3 courts ≈ 375 minutes, or about 6 hours 15 minutes.
Two things make real schedules a little longer than this:
- Rounds don’t divide evenly across courts. 10 teams play 5 games per round; on 3 courts that’s one full wave and one wave with a court idle — unless the next round can start early.
- Rest. If teams need a break between games, some slots can’t be filled even when a court is free.
The generator works this out exactly. Turn on time planning, enter your courts and hours, and it shows the finish time — or, if it won’t fit, how many courts or minutes you’d need. The per-size pages (for example 10 teams) include timing tables for 1, 2 and 4 courts.
Picking a size that fits your day
Work backwards from the hours you have. If you have 4 hours, 2 courts and 20-minute games, you can play about 4 × 60 × 2 ÷ 20 = 24 games. That fits a full round robin of 7 teams (21 games), but not 8 (28). With 8 teams you could split into two pools of 4 (12 games) and add semifinals and a final (3 games) — 15 games in total.
Enter your teams and courts — the generator shows games, rounds and finish time before you commit.
Calculate my eventQuestions
How many games in a round robin with 5 teams?
10 games over 5 rounds. Each team plays 4 games and sits out once.
How many games in a round robin with 6 teams?
15 games over 5 rounds, 5 games per team. Three games are played each round.
How many games in a round robin with 8 teams?
28 games over 7 rounds, 7 games per team.
What is the formula for a double round robin?
n × (n − 1). Every pair plays twice, so it’s exactly double the single round robin.
How many courts do I need?
To play a whole round at once you need n ÷ 2 courts (rounded down). Fewer courts work too — the schedule just takes longer.