Go Ranks

The Basics

Go players have a rank that describes thier playing strength. The ranks start at about 30 kyu (a total beginner) and go down to 1 kyu as a player gets stronger. After 1 kyu, a player becomes 1 dan, and from there the ranks ascend to 6 dan (the highest amateur rank).

Amateur Ranks

30 kyu 29 kyu . . . 2 kyu 1 kyu 1 dan 2 dan . . . 5 dan 6 dan

<- weaker stronger ->

Kyu (pronounced "cue" as in pool cue) and Dan (pronounced like the nickname for Donald) are basically just two different Japanese words for "rank." The same system is used in martial arts like Karate -- a student starts at some high kyu (maybe with a "white belt"), and works his way down to 1 kyu (maybe "brown belt"), and is thence promoted to 1 dan, or "black belt."

Handicapping

One of the nice things about go is that players of different strengths can play an evenly matched game by using a handicap. Instead of starting with the board empty, black (the weaker player always takes black) starts with a bunch of stones on the board. The number of stones black starts with for the game to be even (that is, for there to be an equal chance of either player winning) is the difference in the players' ranks. For example, if player A is 4 dan, and player B is 2 dan, B will "take two stones" from A. If B is 2 dan, and C is 3 kyu, C will take four stones from B.

It works out that this system is nearly transitive; if A gives B two stones, and B gives C four stones, A will be able to give C 6 stones for an even match. Essentially, the handicap system provides an informal empirical definition of the ranks. To find out what your rank is, you just play against another player who knows his rank, and see where you break even.

Players who come to go from other games tend not to want to use handicaps. In many game cultures, for example that of chess, there is a feeling that:

handicaps badly distort the game, and
only a wimp with no self respect would take a handicap anyway.

Handicaps, particularly big ones, do distort the game quite a bit in that they radically change the flavor of the opening. However, perhaps because go openings are less formulaic than chess openings, low (<4 stones) handicap go openings remain interesting.

I've noticed that many chess players feel that if they have a good game, they might beat somone that's quite a bit stronger than them. This may be true in chess (for example, it's not so uncommon for an expert or a master to beat a grandmaster, perhaps in a speed game), but it's not true in go. It would be inconceivable for a 1 dan, for example, to beat a 6 dan. It just couldn't happen (short of a stroke in mid-game). Perhaps for that reason, and perhaps also because in go culture there's a great tradition of respect for stronger players, taking a handicap is not considered shameful in any way.

Confusing Details

Professional Ranks

A few Asian countries (China, Japan, Korea, Taiwan) have professional ranks as well as amateur ranks. These countries have recognized institutions that can grant professional status to players who meet thier criteria. Professional ranks in Japan and Korea start at 1 dan and go up to 9 dan. But these ranks are not on the same scale as the amateur dans.

. . . 6 dan

1 dan 2 dan . . . 8 dan 9 dan

Amateur Professional

For one thing, professional ranks are not tied to playing strength in the same way that amateur ranks are. Professional ranks are conferred by these institutions according to certain rules, and as a result professional rank has as a lot to do with seniority. It's kind of like getting a Ph.D. As a rule of thumb, the strength difference between pro 1 dan and pro 9 dan is only about 2 stones. However, because of the competitiveness of the professional promotion system, many newly promoted 1 dans are very strong; sometimes stronger than some 9 dans.

In general, because all the institutions that grant diplomas make strength one of their main criteria, professionals are very strong. To a first approximation, all professionals much stronger than all amateurs. However, the strongest few amateurs are stronger than the weakest professionals because being professional is a matter of filling a formal requirement. Some talented amateurs who put as much effort into go as professionals do become as strong as a professional, but since they don't go through any professional promotion system, they remain amateurs. Going back to the higher education metaphor, an exceptionally smart and motivated non-academic might well know more about, say, computer science than a run-of-the-mill Ph.D.

The other side of this confusing coin is that there are many different strengths of amateur 6-dan. For example, I can handicap as an amateur 7-dan, but since there is no 7-dan rank, I call myself 6-dan. Meanwhile, there are amateur players who can give me one or two stones. Because there is no 7, 8, or 9-dan amateur, these players are also called 6-dan amateur.

The top professionals are frighteningly strong. A club of about 10 top players in Japan sort of trade the big-money titles among themselves from year to year. In Korea the title-holding club is only about 4 or 5. It's interesting, because the top players don't know more about go; the second-tier players are often as highly respected for questions of go theory as the title holders. But winning under tournament conditions takes a kind of mental toughness that very few people seem to have. It may be that a top player rarely plays a move that's significantly better than what a second-tier pro would have played if asked, but that under tournament conditions they just make fewer mistakes.

International Ranks

Just to make things confusing, there are various differences between what strengths different ranks signify in different countries. Here's a summary:

USA: as described above
Europe: generally 1-2 stones stronger than US ranks (a European 1-kyu might be as strong as a US 1 or 2 dan, and European 5-dans have the same range of strengths as US 6 dans.
Japan: generally 1-2 stones weaker than the US. The Japanese Go Association confers amateur diplomas for a fee, and the professionals who give the examinations tend to err on the side of generosity.
Korea: Totally different. Koreans tend not to start keeping track of their numerical rating until they're quite strong (maybe the equivalent of low kyus in the US). 1 gup in Korea (the Korean word gup is related to the Japanese kyu) is as strong as a US 6 dan, and amateur dans are (last I heard) only given to the very strongest players who win amateur tournaments.
Internet: the ranks on the Internet Go Server (IGS for short) are also totally different. The IGS uses a computerized rating system, and the calibration is about 2-4 stones stronger than US ratings. However, there seem to be very strange intransitivities; pockets of underrated players. For example, a friend of mine plays around 4 or 5 kyu at the New York go club, but 12 kyu on IGS.

Limitations of the Handicap System

Most people consider the handicap system very elegant because it's simple and it works well. However, it's not perfect. For one thing, the value of a stone is not really necessarily constant. For example, against an opponent of constant strength going from 4 stones to 3 stones is a bigger jump than going from 5 stones to 4. Also, there are style interactions that cause intransitivities. Player A might be able to give B at 2 stones, and B might be able to beat C even, but because of the specific strengths and weakness of the players, C might be able to give A two stones.