Belgian Go Federation rating system


How do rating work in Go ?

A rating is an evaluation of a playing strength calculated according to Go games results. In Go, the ratings are represented by "Kyu" and "dan" ranks. A difference in rank of 1 Kyu or dan represents (more or less) a difference of 1 extra stone of handicap on a 19x19 Go board. Beginners have Kyu ratings around 30 kyu. A majority of Go club players are between 20 Kyu and 10 Kyu. Strong players are between 9 Kyu and 1 Kyu and even stronger players are classified between 1 Dan and 9 Dan (strongest). For calculating purpose, the Belgian Go Federation ratings system use more precise values in "points" representing Kyu/Dan values (100 points per rank). The Belgian ratings follow to a large extent the European ratings (European Go Database), but aims to let ratings, especially of beginners, evolve more quickly (e.g., based on club games, smaller board games, using larger weights for games, ...)

I think my rating is inaccurate. What can I do ?

  1. Ratings remain an estimation of a player strength according to results. In order to be able to update a player rating, official game results are needed. Therefore, to get an accurate rating official games have to be played, either tournament games or club games whose results are recorded and sent to the ratings.
  2. Players who have improved and didn't play official games for some time can have a strength significantly different from the one of the rating list.
  3. If your rating strongly differs from your actual strength some manual update might be needed (see below).

What is a manual update and how should it be requested ?

  • Your club president can estimate your rating and send a request to update your rating to the ratings commission if clearly you have become much stronger than your official rating. You can also ask your club president if you think you are in this situation.
  • Up to 5 Kyu your request should be more or less "automatically" granted. For players stronger than 5kyu, the Rating Commission will decide cautiously on the case if there is strong evidence of the claimed strength.
  • The rating commission may also take the initiative to manually update the rating of a player if results suggest that this is appropriate
  • The rating commission has a number of rules of thumb for deciding on manual changes, but reserves the right to judge in the light of all evidence availble, possibly deviating from its habits.

Can I register with a different rank for a tournament than my official rating ?

In principle, you should always register for a tournament with your official rank.

For Kyu players, when registering for a Belgian tournament you can provide a different rating than your official, but only a stronger rating and only if the tournament organizer agrees. This would allow you to be paired according to the rating estimation you provide. Whatever, we suggest you strongly to be cautious with your level declaration - and to provide a higher level estimation only if you are confident that you have at least the claimed strength.

  • If you lose all your games, there will be no evidence that you are stronger than your official rating. It is therefore better to be sufficiently conservative in your rank claim.
  • If your official rank is between -600 and -1, the difference between your claimed rank and your official rank may be at most 1 stone (but do not register as a dan player). Between -600 and -1300, the difference may be 2 stones.

Ratings formula

The Belgian Go Federation rating system is fundamentally an ELO rating system, in the sense that for every won game, the player who wins gains points and goes up in the rating list and the player who loses goes down in the rating list.

Of course the stronger the opponent is, more points there is to gain in case of win and less to lose in case of loss. And vice-versa, the weaker the opponent is, less points there is to gain in case of win and more to lose in case of loss.

Aside from this main feature, the system include a factor which purpose is mostly to stabilize the fluctuation of the ratings as we go higher in the scale. There is also free points given for every game played – whatever there is a win or loss. The value of the bonus is very small at high levels and increase in value as we go down in the rating list. This allows to push every player up adequately to represent improvement.

Points can be translated into the Dan/Kyu ranks (divide the number of points by 100, a positive value is dan, a negative value is kyu). Once a rank is gained, you should lose the points for two ranks before you lose the rank again (e.g., a 2 kyu whose points drop below -300 will become 3 kyu again).

The Belgian rating system has evolved over time. E.g., before May 2001, a different system was in use not based on winning probabilities. The current system doesn't keep any history from before that time. Since June 2001, a new formula is used, based on the EGF ratings model at that time. Since then, several modifications have been made, e.g., to avoid punishing white in handicap games against improving black players (in 2004), to allow games on smaller board sizes, etc. We may not have followed all EGF modifications made over that time.

Weight of the game

The number of points at stake in a rated game depends on various criteria.

As we explained, first of all, on your strength: the stronger you are, the smaller of points you can get or lose by winning / losing your game. But beside this, the characteristics of the game impacts also the number of points at stake. We give a "weight" in function of various criteria:

1. The size of the goban :

  • For a 19*19 game, the weight is (of course) 1.
  • For a 13*13 game, the weight is 0,5
  • For a 9*9 game, the weight is 0.33
  • For other board sizes, the weight is a linear interpolation between the closest board sizes given above.

2. A game played - or not - in a tournament

  • For a tournament game, the weight is 1,2.
  • For a game played (more informally) in a club, the weight is 0,8.

3. Handicap stones.

For games played with a handicap, the weight is:

  • for the player playing with black: 1 - (#h*0,1)
  • for the player playing with white: (1 - (#h*0,1))^2 where x^2 = x*x (since 2004)

4. Game played on-line or face-to-face

The weight is 0,8 for on-line games (including correspondence games) (1 for face-to-face games of course)

5. Thinking time allowance.

The weight is 1 for 75 minutes sudden death, or 60 minutes + 5 minutes for at most 20 stones, or slower.

The faster the game, the less it counts proportionally. F.i., a 45-minute sudden death counts for 45/75 = 60% Minimum time allowance is 40 minutes sudden death or 30 minutes with at most 20 moves in 5 min. In other words, too quick games are not rated.

These criteria are of course cumulative.

Example: the weight for the back player playing a 19*19 tournament on-line game with 3 stones handicap with 60 minutes sudden death thinking time is: 1,0 (19*19) * 1,2 (tournament) * 0,75 (3 stones handicap)* 0,8 (on line)* 0,8 (60 min) = 0,5


Ratings between 100(d-1) and 100d (d>=1) correspond to a rank of d dan. E.g. an average 3 dan has a rating of 250. Ratings between -100k and -100(k-1) (k>=1) correspond to a rank of k kyu. E.g. an average 10 kyu has a rating of -950.

As soon as a player obtains a rating above the maximum rating for his grade, he is promoted. As soon as a player drops 100 below the minimum rating for his grade, he is demoted. E.g. a player increasing from 95 to 101 points is promoted to 2 dan. A 5 kyu player dropping from -490 to -510 remains 5 kyu. Only if his rating decreases further to -601 or less, he becomes 6 kyu.

Ratings are always computed for a complete event. A 1 dan player with rating 99 winning first 2 games and losing then 3 games in a tournament, ending up at 90, remains 1 dan even if he would have a 2 dan rating after the first day of the tournament.

Corrections to grades are possible if new information is added. E.g. suppose a player is -510. He plays a tournament on May 1st and on May 10th. Suppose the organizer of the first tournament reports the results late. As a result of the tournament of May 10th, the player increases to -490, becoming 5 kyu. If later the information of the first tournament is added, both tournaments are recalculated. If this player appears to have lost 50 rating points at May 1st, and ends up at -525 after May 10th, he remains 6kyu.


The above explanation is somewhat simplified and may at some point not correspond fully with the reality of the rating system. The "official" formula is the code as it has been implemented with its many additional rules to cover special cases and exceptions, rather than the high-level explanations of it.