The most common reason community tournaments run late is not technical problems or no-shows. It is that the organiser never worked out how many rounds the format needed before opening registration. This guide collects the formulas for every common format, puts them in tables, and shows how to turn them into a realistic schedule.
Matches versus rounds
Two numbers matter, and they are easy to confuse:
- Matches is the total number of games played. It tells you how much admin work, reporting and streaming you are signing up for.
- Rounds is how many sequential waves of matches you need, assuming all matches in a round run at the same time. It tells you how long the event takes.
If you have enough servers or stations to run every match in a round simultaneously, event length depends on rounds, not matches. If you only have one stage or one broadcast, it depends on matches.
The formulas
| Format | Matches | Rounds |
|---|---|---|
| Single elimination | n − 1 | ⌈log₂ n⌉ |
| Double elimination | 2n − 2 (or 2n − 1 with a reset) | about 2 × ⌈log₂ n⌉, plus the final |
| Round robin | n(n − 1) ÷ 2 | n − 1 if n is even, n if n is odd |
| Swiss | (n ÷ 2) × rounds | you choose; ⌈log₂ n⌉ is typical |
Here, n is the number of teams, and ⌈log₂ n⌉ means “how many times you double 1 before reaching or passing n”. For 16 teams it is 4, for 20 teams it is 5, and for 32 teams it is 5.
Matches by team count
| Teams | Single elim | Double elim | Round robin | Swiss (log₂ rounds) |
|---|---|---|---|---|
| 4 | 3 | 6–7 | 6 | 4 |
| 6 | 5 | 10–11 | 15 | 9 |
| 8 | 7 | 14–15 | 28 | 12 |
| 10 | 9 | 18–19 | 45 | 20 |
| 12 | 11 | 22–23 | 66 | 24 |
| 16 | 15 | 30–31 | 120 | 32 |
| 32 | 31 | 62–63 | 496 | 80 |
| 64 | 63 | 126–127 | 2,016 | 192 |
Two things jump out. Round robin grows very fast: doubling the field roughly quadruples the matches, which is why it is almost always used for groups of four to eight rather than whole events. And Swiss sits in a useful middle ground, giving every team several matches without the explosion of a full round robin.
Rounds by team count
| Teams | Single elim | Double elim (approx.) | Round robin | Swiss (typical) |
|---|---|---|---|---|
| 8 | 3 | 6–7 | 7 | 3 |
| 12 | 4 | 8–9 | 11 | 4 |
| 16 | 4 | 8–9 | 15 | 4–5 |
| 24 | 5 | 10–11 | 23 | 5 |
| 32 | 5 | 10–11 | 31 | 5–6 |
Turning rounds into hours
To estimate event length, you need a realistic slot length per round. That is not the length of a match. It is the length of a match plus everything around it:
- Match time. Estimate from experience. A competitive Valorant or Counter-Strike 2 map commonly runs 35 to 50 minutes; a Rocket League best-of-five is often 30 to 40 minutes; a fighting game set is usually under 15.
- Series length. Multiply by the number of games in the series. Use the expected number, not the maximum: a best-of-three averages about 2.5 maps.
- Overhead. Add 10 to 15 minutes for lobby setup, check-in, score reporting and breaks between maps.
- Buffer. Add 10 to 20 percent for technical pauses and the one match that always runs long.
Example: a 16-team Valorant event, best-of-one until the semi-finals, then best-of-three. Single elimination needs 4 rounds. Rounds one and two are best-of-one at roughly 45 + 15 = 60 minutes each. The semi-finals and final are best-of-three at roughly 2.5 × 45 + 15 ≈ 130 minutes each. Total: 60 + 60 + 130 + 130 = 380 minutes, plus a 15 percent buffer ≈ 7 hours 15 minutes. Running the same event as double elimination would take roughly twice as long, which is a two-day event for most volunteer teams.
The constraint most people forget: stations and servers
The round counts above assume every match in a round can run at the same time. At an online event that is usually true, because each team hosts or joins its own lobby. At a LAN or a broadcast-first event it often is not. If you have 4 stations and round one has 8 matches, round one takes two slots, not one.
The rule of thumb: the number of slots per round is the number of matches in that round divided by the number of stations, rounded up. Add those slots across all rounds to get your real schedule.
Choosing a format from the numbers
- One evening, many teams: single elimination.
- One full day, 8 to 16 teams: double elimination, or Swiss into a short playoff.
- A weekly league over a season: round robin, one round per week.
- Large field, several matches per team, limited days: Swiss.
Our format comparison summarises these trade-offs, and the single vs double elimination guide goes deeper on the two knockout formats.
Planning checklist
- Pick a team cap before registration opens.
- Look up the round count for your format and cap.
- Estimate slot length: match time × expected games + overhead.
- Multiply, then add a 15 percent buffer.
- If the result does not fit your window, change the format or cap, not the buffer.
With the numbers settled, building the bracket is the easy part. Open the generator, paste your teams and pick a format.