How Many Rounds in the Swiss System: a table by field size

The main question when preparing a Swiss tournament is how many rounds to play. Too few and the winner is random; too many and the tournament drags without benefit. There's a simple rule and a ready table to pick precisely. Let's cover the logic and give numbers for any size.

A ready round-count table

Players	Rounds
up to 8	4-5 (or round-robin 7)
8-16	5
17-32	6
33-64	7
65-128	8-9
129-256	9-11

Why exactly that many

The logic is simple: to reveal a single winner, the round count should grow roughly like the binary logarithmof the field. Each round roughly halves the group with the maximum score, so 16 players are "separated" in 5 rounds, 32 in 6, 64 in 7, plus a little slack for tied scores.

Hence a pleasant consequence: the round count grows very slowly. Even a mass tournament of a hundred people needs only 8-9 rounds - one day. That's what makes the Swiss system the standard for big amateur events.

What if you get the number wrong

Too few rounds and several players score the same, so the winner is decided only by the Buchholz coefficient, which is less obvious. Too many and the last rounds pair leaders whose fate is already sealed, while the tail plays on without suspense.

Use the table above and you won't go wrong. The round count is set once when you create the tournament in the bot, and the bot keeps the pairing correct. How the tie-break works is in the article on the tournament FAQ.

Set the rounds and start

Once you know the field size, take the rounds from the table, create a tournament in the bot and play. The bot does the rest.

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Frequently asked questions

How many rounds do I need in the Swiss system?

Guide: 8-16 players - 5 rounds, 17-32 - 6, 33-64 - 7, 65-128 - 8-9. The count grows like the binary logarithm of the field, so even a hundred people play just 8-9 rounds.

Where does that number come from?

Each round roughly halves the group with the maximum score. To leave a single winner you need about log2(players) rounds plus a little slack for tied scores.

Can I play fewer rounds to go faster?

You can, but then several players score the same and places are decided only by Buchholz - less obvious than a clean win on points. For a short event that's acceptable.

What if there are very few players - 6-8?

For such a group you can use a round-robin (everyone plays everyone), 5-7 rounds and the fairest result. Or a Swiss of 4-5 rounds if time is tight.

Does the bot pick the round count itself?

You set the round count when creating the tournament, using the table. Then the bot keeps the pairing correct for the chosen number of rounds.

Missing a feature? Message the developers

The bot is constantly improved based on real tournaments. If you need a feature that isn't there yet, message the developers right inside the bot with the /support command. Many features appeared exactly because organizers asked for them, and useful ideas get added quickly.

What to read next

Plans by size - 16, 20 and 30 players. The tie-break - tournament FAQ. General prep - how to organize a tournament.