Why the McMahon System Is Ideal for Go
Under the classic Swiss system, strong and weak players have to wait several rounds before facing opponents at their level. The McMahon system solves this problem: each player starts with an initial score based on their rank (kyu/dan), so from the very first round they face players of a similar level. It is the standard format in almost all Go tournaments worldwide.
- Initial score by rank: Dan-ranked players start at a higher level, and kyu-ranked players at a lower level, divided into groups.
- Tied matches from Round 1: Fewer wins by default and fewer blowouts.
- It works with many players and few rounds: Ideal for one-day tournaments.
How to Organize a Go Tournament, Step by Step
- Create a free account. Sign up in less than a minute; no credit card required.
- Create a tournament and choose the McMahon format. Give it a name, the dates, and the number of rounds.
- Add players by rank. Enter the level (for example, 5k, 1d, 3d) to calculate the starting score.
- Configure the bands and the order of transmission. Sort the list; the system assigns each player to their McMahon faction.
- Generate the matchups and share the standings. Publish the results round by round with automatically updated standings.
A practical example: a club tournament with players of very different skill levels
Imagine a club tournament with 40 players ranging in rank from 15 kyu to 3 dan. Under the McMahon system, players are divided into groups: for example, all players with a dan or higher move to the top group with an initial bonus of 20 points; players between 5-kyu and 1-kyu receive 10 points; and players from 15-kyu to 6-kyu start with 0. This way, a 3rd dan and a 1st dan can face each other in the first round without the result being absurd, while a 15th kyu takes a few rounds to move up to the mid-level players. With this initial bonus, a 5- or 6-round tournament is usually sufficient to produce a reliable final ranking; in a pure Swiss system where everyone starts at 0, many more rounds would be needed for the pairings to “discover” on their own who is strong and who is not.
Tips for Pairing Well with McMahon
- Define the categories before the tournament begins: Decide how many extra points separate each rank bracket (for example, one point for each rank difference) and post this information so that players understand the scoring system.
- Set a minimum threshold (the “McMahon barrier”): Weaker players should not be dragged down to a negative score; a minimum score must be established so they can continue to compete with a real chance of winning.
- Write down each player's actual ranking, not the one you remember off the top of your head: Use their ranking with the federation or their ranking from their most recent competition, if available, to ensure that the initial bonus is fair.
- Decide on the game's scoring rules in advance: Japanese rules (territory + prisoners) or Chinese rules (area); this doesn't change the matchups, but it prevents arguments on the day of the tournament.
Common Mistakes When Organizing a McMahon Tournament
- Mixing very different categories without a handicap adjustment: Pitting an 18-kyu player against a 4-dan player without a komi results in a completely lopsided game, even though the McMahon pairing is correct on paper.
- Playing very few rounds across a very wide range of skill levels: When there is a large gap between the weakest and strongest players, three rounds are not enough: the initial bonus never fully balances out the players' actual skill levels.
- Do not set a minimum score: Without a minimum (the “McMahon limit”), a player on a losing streak ends up with a negative score that excludes him from any competitive matches for the remainder of the tournament.
- Forgetting to update the standings before the tournament: A player who has moved up several levels since their last tournament may end up being seeded in a lower category, which also distorts the matchups for their opponents.
McMahon vs. the Classic Swiss System
The key difference lies in the starting point. The pure Swiss system (the one used in chess) starts all players at 0 points and takes into account only what happens within the tournament itself; it takes quite a few rounds before the pairings truly reflect each player’s skill level. The McMahon system starts with information that is already known in advance—each player’s kyu/dan rank—and converts it into an initial bonus. This makes it ideal for Go clubs, where there is often a wide and well-known difference in skill level among participants: within just a few rounds, the standings already separate the strong players from the weaker ones—something for which a pure Swiss system would require far more rounds than a single-day tournament allows.
Frequently Asked Questions
Is it really free to organize a Go tournament?
Yes. You can create and manage your Go tournament for free, including McMahon pairing, rating tiers, and real-time standings.
What is the McMahon system, and how does it differ from the pure Swiss system?
This is a variation of the Swiss system in which each player starts with an initial score (the “McMahon number”) based on their ranking, rather than everyone starting from 0. This ensures that matchups are balanced from the very first round, which is important when players of very different skill levels are mixed together in the tournament.
How is each player's starting score calculated?
Ranks are grouped into bands (for example, dan-level players at the top, middle-kyu players in the middle, and lower-kyu players at the bottom), and each band receives a different bonus. The higher the rank, the greater the initial bonus compared to the lower band.
What is the difference between “kyu” and “dan” in the tournament?
"Kyu" refers to the beginner to intermediate level and is counted downward (20 kyu is lower than 5 kyu); "dan" refers to the advanced level and is counted upward starting at 1 dan. Both ranks are used to determine each player's band and initial bonus.
Do I need handicap stones for tournament games?
This is common in clubs where there are large differences in skill level: handicap stones even out the difference in skill between opponents so that the game remains competitive, regardless of the scoring adjustment that the McMahon system already applies in the rankings.
How many rounds are needed to obtain a reliable ranking?
Thanks to the initial seeding bonus, a McMahon tournament typically requires significantly fewer rounds than a pure Swiss tournament to produce a reliable final ranking; usually, 5 to 6 rounds are sufficient for an average number of participants.
Does the tool score each match (territory or zone)?
No; the scoring of games (by territory and captives according to Japanese rules, or by area according to Chinese rules) is determined by the club and is carried out on the board. The tool manages pairings according to the McMahon system, groups, and the tournament standings, but it does not handle the scoring for each individual game.
Can I use this same system for a game other than Go?
The McMahon format is specific to Go, but the tool also offers league, cup, knockout, Swiss, and Americano formats, which are compatible with chess, padel, and other sports and games.
Can I upload the results to the EGD (European Go Database)?
Yes. The tool exports the list of players in the official EGD format: enter each player's ranking, country, and club, and download a file ready to be uploaded to EGD Admin.
What happens if there is an odd number of players or if someone drops out halfway through the tournament?
If there is an odd number of players, the tool automatically assigns the bye round with the corresponding win; no action is required. And if a player withdraws, you must mark them as withdrawn on the organizer’s page: they will no longer be paired in subsequent rounds, but will retain their points and the games already played in the standings.
Does the tool assign who plays Black and who plays White?
Yes. In McMahon and Swiss pairings, color is assigned automatically, with the goal of ensuring that each player finishes the tournament with a similar number of games played with each color and avoiding too many consecutive games with the same color. This is our own balancing heuristic, not the official color-assignment rules of any federation; for tournaments that require very strict control over colors, please review it before publishing the pairings.
Create your Go tournament now
Organize your next Go tournament using the McMahon pairing system in just a few minutes. Create your free account or Discover the competition to see how it works.