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" values. 1 Kyu represents (more or less) a difference of 1 extra Go stone 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.

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 (tournament) games have to be played.
  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 6 Kyu your request should be more or less "automatically" granted. For players stronger than 6kyu, the Rating Commission will decide cautiously on the case if there is strong evidence of the claimed strength. Players that didn't play or report results for some time can have a strength significantly different from what is in the rating list.

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. 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 loose 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. Using a mapping function, points are calculated in a way that allows them to be translated into the Go Dan/Kyu universal rating system. Up to May 2001, a rather complicated formula was used to compute ratings. In its meeting of May 2001, the rating commission decided to simplify the formula to make it mathematically better and more understandable. Since June 2001, a new formula is used. It was originally 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, to alloax games on smaller board sizes, etc. We may not have followed all EGF modifications made over that time.


Ratings between 100(d-1) and 100d (d>=1) correspond to a grade of d dan. E.g. and average 3 dan has a rating of 250. Ratings between -100k and -100(k-1) (k>=1) correspond to a grade of k kyu. E.g. and 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. If his rating decreases further to -601, 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.