Free tool
Swiss tournament rounds calculator
How it works
Enter your player count. The calculator returns log2 of the players, rounded up, as a planning estimate: if every game were decisive, each round would halve the players on a perfect score. 24 players give 5 rounds. Draws, byes and tie-breaks decide the real standings, so no player count guarantees a single winner. The tool also shows the most rounds a field can play without anyone meeting twice.
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- Method shown below
- 3 cited sources
The estimate is log2(players), rounded up: if every game were decisive, each round would halve the players on a perfect score. Real events have draws, so the estimate does not promise a single winner. Publish the tie-break order before round 1, and fit the rounds to the hall with the tournament time planner.
ResultUpdates as you type
Planning estimate, rounds
5
A starting point. Draws and byes can still leave a tie for first.
Most rounds, no rematch
23
A full round robin. Beyond this someone would meet a player twice.
Boards per round
12
Every player has a game each round.
One extra round (6) still avoids rematches. It can change the standings, but ties at the top can still happen.
How it works
The method behind the numbers
Formula
Planning estimate = ceil(log2(players)). Most rounds without a rematch = players - 1 (even field) or players (odd field)
A Swiss event pairs players on similar scores each round and nobody is knocked out. With only wins and losses, the number of players on a perfect score would halve each round, so ceil(log2(players)) rounds is enough for one perfect score to be possible. Treat that as the number to start from. It is a planning estimate and not a promise.
More rounds change the odds, not the need for a rule. In a fourth round A and C cannot meet again, so each plays someone on 2 points. If both win, they finish on 3.5 and tie again. FIDE’s tie-break regulations, effective 1 March 2026, have the chief arbiter publish the tie-break list before the tournament starts. Do the same: choose the tie-breaks before round 1 and print them on the event notice.
The other limit is the pairing rules. FIDE’s basic Swiss rules (C.04.1, effective 1 February 2026) declare the number of rounds beforehand and do not let two players meet twice. An unpaired player gets a bye that scores as a win unless the event rules say otherwise, and no player receives a second pairing-allocated bye. So an even field of n players can run n - 1 rounds at most and an odd field n rounds. Two players have exactly one round. Three players can have three, each sitting out once. A pairing program can run out of legal pairings before that ceiling, so treat it as an upper bound.
| Round | Pairing | Result | Leaders afterwards |
|---|---|---|---|
| 1 | A-E, B-F, C-G, D-H | The first-named player wins every game | A, B, C, D on 1 |
| 2 | A-B, C-D, E-F, G-H | A and C win, as do E and G | A, C on 2 |
| 3 | A-C | Draw | A and C on 2.5 of 3; no other player can pass 2 |
Hypothetical event. Players A to H are labels, not real people. A fourth round would give a tie again if A and C both won.
| Question | Answer it with | What you get |
|---|---|---|
| How many rounds to start from? | This calculator | The log2 estimate and the no-rematch ceiling |
| Can the pairings stay legal that long? | The no-rematch ceiling here, then the Swiss pairing guide | The most rounds before someone repeats an opponent |
| Will the rounds fit the hall? | The tournament time planner | Round and event time at a stated move count |
| Who is ahead when scores tie? | A tie-break order printed before round 1 | A trophy order that does not depend on arguments |
Corrected 16 October 2026: an earlier version said the log2 minimum produces a clear winner and recommended extra rounds for prizes. Neither holds once draws are possible, so the figure is now a planning estimate and the page shows the longest event without a rematch.
Worked example
The steps with real numbers
Illustrative figures, worked the way the tool works them. Put the same numbers into the tool above to check.
Back to the toolDraws break the arithmetic. Take eight players and three rounds, the log2 estimate. Round 1 is decisive on every board, leaving A, B, C and D on 1 point. In round 2 the winners meet and A and C win. In round 3 the two leaders, A and C, play and draw. Both finish on 2.5 out of 3, and no other player can pass 2. Nobody scored 3. This is a hypothetical event and the point is the arithmetic.
The same job inside ChessCore
Chess batch scheduling
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Questions
Frequently asked questions
How many rounds for 16, 32, or 64 players?
The log2 estimates are 4, 5 and 6 rounds, because those field sizes are powers of two. They are starting points. A single draw between the leaders can leave a tie for first at any of them, so decide the tie-break order first and then fit the number of rounds to the hall with the time planner.
Can I add rounds to make sure there is one winner?
No. More rounds can separate the leaders, but a draw between them in the last round can always produce a tie. Only a published tie-break order, or an extra playoff game you announce in advance, settles a trophy.
What is the most rounds a small field can play?
Without a rematch, 2 players have 1 round, 3 players have 3 rounds with one bye each, 6 players have 5 rounds and 7 players have 7. Those are full round robins, so the pairing is forced in the last rounds. For small fields a round robin is usually simpler than a Swiss.
Does a bye count as a game played?
No. An unpaired player has no opponent and no colour. Under FIDE’s basic rules the bye scores as many points as a win unless the event rules state otherwise, and the same value applies to every bye. The tie-break regulations have their own rules for unplayed rounds, so publish how byes are treated before round 1.
Why not just run a knockout instead?
A knockout sends half the field home after one game, which is a poor experience for students and parents who travelled for a day of chess. A Swiss gives every player a full schedule of games against similar scores, which is why it dominates amateur and scholastic chess.
What happens when two players have the same final score?
The tie-break list decides the order. Common ones compare the strength of the opposition, such as Buchholz, or use direct encounter first. The chief arbiter publishes the list before the tournament starts, and each tie-break is applied in turn to the players still tied.
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