Go ranks and ratings

The traditional board game Go (igo, baduk, weichi or weiqi) has a number of national, regional and online systems of measuring levels of skill, as ranks and ratings. A go rank is comparable to a rank in some Asian-originated martial arts. A rating rigorously calculated on the basis of game results is less traditional (common on go servers).

Levels of players are defined by ranks in Go. Strictly speaking, we should only say rank, but not rating or level or grade. The rank system is tabulated from the lowest to highest ranks:

Double-digit kyu, 10-30k : Introductory
Single-digit kyu, 1-9k : Elementary to Intermediate
Amateur dan, 1-7d : Advanced
Professional dan, 1-9p : Expert

Origin

From about the sixteenth century, the Japanese formalised the teaching and ranking of Go. The system is comparable to that of martial arts schools; and is considered to be derived ultimately from court ranks in China.

Kyu (pronounced like the letter "Q" and abbreviated as "k") is the first stage. This stage is very broad, in which there are full of different levels of players in this stage. Traditionally a newcomer starts at 30 kyu (30k), and proceed numerically downward as strength increases to 1 kyu.

Ranks between about 10k and 30k have very limited usefulness and meaning since there are discernible differences in each level. It is not surprising to see a 25k defeat a 15k player, so these ranks are of little significance. They are mainly used in teaching, to mark their learning progression.

The requirement of a "rank up" at this stage is very loose. Learning a few basic things or concepts may guarantee you a jump to another rank. That is why players in the weak double-digit kyu ranges (DDK, 10-30k) often progress very quickly, especially young children. A jump from 30k to 10k is not abnormal and it could happen within weeks or even days (for quick and modest learners).

Starters learn and play on 9×9 boards first. As they progress, they start to play on a 13×13 boards. A 19×19 board is the standard size in Go world. Every learner has to play on this board eventually.

Introductory: 10k-30k

This is a double digit kyu (DDK) world. The ranks here are reserved for newbies or starters. When you first come into the world of Go, you start at 30k traditionally. Note the word "traditionally". 30k is just the normal standard. Some may say you start at 20k. Some may jokingly say you start at even 40k or 50k (non-existent ranks)

Elementary: 5-9k

After one attained 9k or better, one has come into next stage in kyu, ie single digit kyu world (SDK, 1k-9k). This is the lower class of the single digit kyu world.

Unlike the double-digit kyu (DDK) world, the ranks here are much more stable. Each rank counts heavily and means something. A "rank up" at this stage is much much harder than you could think of. One may spend weeks or even days to jump from 30k to 10k. However it requires many weeks or several months merely to get 1 rank promotion. The smaller the rank number of kyu, the harder one jumps into. Although it is not impossible, it is uncommon for a 9k player to defeat a 1k player.

The progression from DDK to SDK is a significant turning-point for learners as you have gone through all the very basic learning processes and become a qualified Go player. It is said "you are not a Go player if you cannot attain a SDK". You can see how high people treat a SDK rank, as opposed to a DDK rank. Nevertheless SDK Go players within the lower-class are nothing more than beginners in Go. Although they have gone through all the very basic learning materials & concepts, it is hardly enough. Go is one of the deepest games - easy to learn, hard to play (well). Unlike DDK players, lower-class SDK players know how to play "in Go sense". Still their moves are very crude & full of mistakes, in the eye of advanced players.

Unlike the DDK world, there is rarely a SDK player who will often play on a 9×9 or 13×13 board. All players focus on 19×19 boards at this stage.

As to computer Go, the best computer Go are still stuck around the lowest-class of SDK, ie 8-10k. Some of computer Go are even outside SDK ranges, which are very disappointing. Unlike other board games like chess, computer Go is only a good opponent for very elementary SDK Go players or DDK players.

Intermediate: 1-5k

It comes to the upper class of the single digit kyu (SDK) world. Average club-level players are taken to be around 4-6k.

Although it is just a few ranks of progression, it is already meant a lot for Go players. It is never easy to attain such ranks. This upper-class of SDK is a proof of Go strength. It may take a good year or more to come to this upper class. They have gone through a lot of training and practice. They know how to make use of each stone, but not to waste them as many beginners tend to do. They start to read each sector of the board as a whole. They have a broader mind to play Go, but not to play in narrow minds which beginners tend to do. There are a lot of Go senses in their matches.

To go even further, normal players may need years to decades to get out of kyu ranking stage. Many players never get out of it though.

There is a tendency that intermediate players do not like to play with DDK players. Apart from the reason that they are still too weak to compete even with the highest 9-stone-handicap, they may fall into bad habits if they play too many low-grade games. Their Go sense will be weakening when, say, they involve in some very silly plays or tactics which can trap DDK players only.

Advanced: Amateur Dan

One rank higher than a 1 kyu player will bring you into another stage - (amateur) dan. Dan (abbreviated as "d") ranks are for expert or amateur players. Unlike kyu ranking system, Dan ranks ascend numerically with strength, to a normal high of 7 dan. 8 dan is not really a rank. It is rather a special and honorary title. A small number of 8 dan can be attained by winning some of the national tournaments.

The 1 dan, or shodan, rank is achieved when all elementary and intermediate go concepts are mastered, implying a general competence in the game. This usually requires a number of years of playing seriously, though exceptionally talented players have risen from first exposure to the game to shodan in a year.

Although the difference in skill levels between 1k and 1d is not meant to be huge (it is more or less the same between 1k and 2k, or 3k and 4k), it is the transition from 1 ranking symbol into another makes people feel more glorious. Recognition as a dan player is the ambition of most average club-level players.

In Japan, before the year 2001, only amateur ranks up to 7 dan were recognised. Now amateur ranks are recognised up to 8 dan. 8 dan is a special and honorary title for amateur which is awarded to the winner of the World Amateur Go Championship. Within the European Go Federation, ranks are recognised up to 7 dan. The American Go Association currently recognizes rankings up to 6 dan amateur.

Expert: Professional Dan

The professional dan ranking system is similar to amateurs dans but with more ranks. For historical reasons, it ranges from 1-dan (entry-level expert) to 9-dan.

To distinguish between pro dan and amateur dan, the former is often written "p" (sometimes called ping) and the latter "d". There is no such abbreviation in the past, and this is NOT generally used as an abbreviation beyond the Internet, where it is common, but not universal.

Each dan rank has its own name. The following are the Japanese names for each dan rank:

* Shodan 1-dan (entry-level expert)
* Nidan 2-dan
* Sandan 3-dan
* Yondan, Yodan 4-dan
* Godan 5-dan
* Rokudan 6-dan
* Nanadan (Shichidan) 7-dan
* Hachidan 8-dan
* Kudan 9-dan
* Judan 10-dan

More on Go ranking system

Increasing efforts with diminishing returns

What the whole list of go ranks cannot show is the asymptotic shape of the skill improvement over time (increasing efforts with diminishing returns). It is summarized in the saying "(Go is) Easy to learn and difficult to master".
Here's some examples to illustrate the concept of "increasing efforts with diminishing returns":

* A newcomer could rush through from 30k to about 11k in a month - possibly a week if the player is a serious learner or has a mind for the game.
* However a player might take several months to a year attain a rank up when it reaches a single-digit kyu. The lower the single-digit kyu, the more time and efforts are required for a rank up.
* It would take even a year to a decade (if unusually talented) to reach amateur 1 dan (if at all!).
* It's hard to imagine how hard one can progress from one pro dan to another pro dan. It requires much more efforts and talents, great enthusiasm and dedication. You have to spend full-time to study Go.

The handicap between these stages would be about 9 stones each, but the time to achieve the levels is highly uneven, even if the effort might have been the same. Few make it to a 5 dan amateur ranking (i.e. ELO 2500 in Europe) and only after great enthusiasm and dedication, taking many, many years. This level reflects a deep and subtle level of understanding of the strategy of the game, coupled with a keen, well-practiced ability to judge abstruse, complex tactical situations.

How to become a professional

Professional dan rankings are normally awarded in Japan, China, South Korea or Taiwan, through one of the professional go associations, most notably, the Hanguk Kiwon (Korea) or Nihon Ki-in (Japan).

The attainment of professional qualification differs in different countries:

* In China a few amateurs are given the 1p grade as probationers, on the basis of success in amateur tournaments.
* In Japan student professionals are called insei, and have to play in internal insei competitions to qualify; mostly they are adolescents, and must decide whether to continue based on their chances of a career in go, or go to university. Insei rarely take part in amateur events, but some of the top amateurs are ex-insei.
* In South Korea four amateurs become professional every year, at the top of a ferocious league system of 80 aspirant pros. Once within the professional system, promotion is based on game results.

The game of go requires study from an early age, should one wish to become a strong professional player. In order to qualify as a 1 dan professional (1p), one must have deep resources of game experience and study. Tactically, professionals thoroughly understand good shape, tesuji, and life and death. Pros mostly have similar levels of pure technical skill. They differ more in positional judgement: deep evaluation of future game positions and a great variety of tactical and strategic means to obtain that imagined future position are requirements for professional players. It is of basic importance for a player to know whether they are behind or have the advantage, because it influences the risks that should be taken and subsequently the strategies chosen in a game.

Knowledge of opening patterns (fuseki) and tactical patterns (joseki) is a by-product of years of study and playing Go; memorization is not the basis for strong play. Fuseki and joseki knowledge is far less central in Go than openings are in Chess. The decisive part of the game, resulting in win or loss, may occur 100 moves or more later.

The differences between professional levels are much smaller: perhaps of the order of 3 to 4 handicap stones between an average 1p and a prime 9p, as a rough rule of thumb. Thus the difference between professional dan levels corresponds to one-third or one-fourth handicap stone, and the strength of a typical professional will correspond to that of an amateur 9-dan (if it existed) or higher in theory.

Each country has different rules for promotion. Ranks may therefore differ somewhat from country to country. Generally Asian professionals are stronger than Western or European professionals.

Professionals may also differ from actual strength for a number of reasons, including promotion not keeping up with actual gains in strength, or the fact that professional ranks, unlike kyu or amateur dan, may rise but never fall (even if they grow weaker). This has posed some of the problems. There are currently over one hundred people who have the rank of 9p (the highest professional rank), though many of them no longer play competitively, due to age. A further distinction is that some 9p players regularly hold titles, some won some titles, some entered the title leagues and many 9p never had the luck to achieve any of above.

To make the case look even worse, there are some instances where a low pro dan can beat some of the highest pro dan, although it is not too common. At the extreme, it is possible for a 1p to beat a 9p. For example, Abe Yumiko 1-dan beats 9-dan.

The Japanese Oteai system, dating back to 1924, was reformed in 2004 to alleviate some rank inflation that had crept in over the years. Today's system uses various benchmarks; for example, winning certain tournaments or a certain number of games, to be promoted a rank. The Korean system has also been similarly changed in the past few years.

Pro and amateur dan

In theory, professional dans should beat all levels of amateur dans. In reality, the very top amateurs have proved very strong, even against professionals, though they do not have an official, professional rank. The conventional wisdom is that such players may achieve some of the insight of a pro, though perhaps not the detailed knowledge.

In China, Japan, and Korea, there are two distinct ranking sets, one for amateur players and one for professional players (who receive a fee for each game they play, bonuses for winning, and fees for other related activities such as teaching).

In the Japanese professional ranking system, distinction between ranks was traditionally considered to be roughly one third of a handicap stone (making the difference 3 pro dan equal to one amateur dan). The strength of new professionals (1 dan) was usually comparable to that of the highest ranked amateurs. Currently the professional ranks are assumed to be more bunched together, covering not much more than two amateur dans; so that pro 1 dans win some games against 9 dans. There are also a number of amateur players acknowledged as having pro 6 dan understanding of the game.

In South Korea, there are several amateur systems in use, with the recent introduction of official 7, 6 and 5 dan amateur ranks, each of which is somewhat stronger than the corresponding European grade. A 7 dan amateur will have won three national events, and will be effectively of lower-ranked pro standard. The older gup system does not easily match others. In practice, in Korean clubs, grades may be worked out against the resident stronger amateur.

In Taiwan a distinctive system of pro dan ranks is used, with the order reversed (so that 1 dan is the highest, 9 dan the lowest).

In Germany and The Netherlands a "classes"-system (German: "Klassen") was established. It comprised a further subdivision into Kyu/Dan halfgrades with classes 18 and 17 = amateur 1 dan with the 17 being on the stronger side. It is still in use for club ladders etc. where you get promoted or demoted after a won or lost game, respectively.

Go rating with ELO

As in other sports where it is not practical to hold an all-against-all championship to establish who is strongest (Chess, statistical Backgammon, physical Racquetball etc.) a statistical method is employed. The ELO rating system is nowadays often used in Go (see also external links). An average 1 dan should have Go Rating about 2100 and the difference between grades is set to 100. Hence, a rating of 2100 would coincide with an amateur 1 dan who has a 2/3 winning chance against just anyone with a recent rating of 2000 (e.g. an average 1 kyu, a recently improved 2 kyu or a 1 dan who has lost many games and so rating points).

Similarly, one only has a 1/3 winning chances against any player with a recent ELO rating 100 points higher than oneself. Here one can see the difference between ranks kyu/dan, being the highest personal achievements and an actual rating. A player having been 3 dan 15 years ago will know the necessary strategies and concepts for teaching weaker players, but when it comes to actual play this person will certainly lose rating points when again entering the tournaments (where the rating points are measured) against players with the same grade.

Winning Probabilities

The rating indirectly represents the probability of winning against other rated players. This probability depends only on the difference between the two players' ratings as follows (based on a normal distribution with a standard deviation of 286):

rating probability
difference of winning
---------- -----------
400 .919
300 .853
200 .758
100 .637
50 .569
0 .500
-50 .431
-100 .363
-200 .242
-300 .147
-400 .081

Converting Elo Ratings into Go Ranks

The Elo system can be used establish a Go grade (kyu/dan) by a national promotion commission or implement Go ranks on Go servers (on the internet).

Points Go rank
------ -------
2900 9 pin (9 dan professional)
2780 5 pin (5 dan professional)
2660 1 pin (1 dan professional)

2600 6 dan (amateur)
2500 5 dan
2400 4 dan

2300 3 dan
2200 2 dan
2100 1 dan

2000 1 kyu
1900 2 kyu
1800 3 kyu

1500 6 kyu
1000 11 kyu
500 16 kyu
100 20 kyu

0 21 kyu
-100 22 kyu
-200 23 kyu etc.