Swiss Tournament Planner
How many Swiss rounds a field needs, how long it will take, and — the number that actually matters — how many players will be tied on the cut line.
Where the field is expected to finish
Assuming every match is a coin flip. Real Swiss pairs winners against winners, which bunches the field toward the middle — so treat the bubble figure as a lower bound on how crowded it will actually be.
Why the rounds are what they are
- The number of rounds is arithmetic, not convention. Each round at most halves the unbeaten players, so you need 2^R to reach the field size — three rounds for eight players, four for sixteen, five for seventeen.
- That jump at every power of two is why a 17-player event runs an hour longer than a 16-player one for the sake of a single extra entrant.
- The record spread here assumes every match is a coin flip. Real Swiss pairs winners against winners, which bunches the field toward the middle more than this curve shows — treat it as a lower bound on how crowded the bubble will be.
- What decides whether an event runs smoothly is not the cut size but how many players are tied ON the cut line. That is the number this works out.
- An odd field means one bye every round. A bye normally counts as a win, which is worth stating before the event rather than after.
How to use
- Enter the number of players and the cut you want.
- Read the suggested rounds, or override them.
- Check the record table for how crowded the bubble will be.
Frequently asked questions
How many rounds does a Swiss event need?
It is arithmetic, not convention. Each round at most halves the players who are still unbeaten, so you need 2^R to reach the field: three rounds for eight players, four for sixteen, five for seventeen. That jump at every power of two is why a 17-player event runs an hour longer than a 16-player one for the sake of one extra entrant.
Why does the record table not match my last event?
Because it assumes every match is a coin flip, and real Swiss does not work that way — it pairs winners against winners, which bunches the field toward the middle more than the curve shows. Treat the bubble figure as a lower bound on how crowded it will actually be, not a prediction.
What actually decides whether an event runs smoothly?
Not the cut size — how many players end up tied ON the cut line. Sixty-four players over six rounds gives one at 6-0 and six at 5-1, then about fifteen at 4-2 fighting over a single remaining place on tiebreakers. That is where the arguments happen, and it is the number this works out for you.
Does a top 8 need fewer rounds than finding one winner?
In principle yes, by the same halving argument — but only as a floor. Ties mean real events almost always play more rounds than the minimum, because the point is separating the cut cleanly rather than merely reaching it.
What happens with an odd number of players?
One bye every round. A bye normally counts as a win, which is much better stated before the event than argued about afterwards. The planner tells you how many byes you will need to hand out in total.
Why must the cut be a power of two?
Because a single-elimination bracket halves each round. A top six needs two players to sit out the first round, which is workable but needs deciding in advance — so anything other than 2, 4, 8 or 16 is flagged.
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