Tuesday, 31 January 2012

Defence theory(6): Tile risk table

Source: http://blog.jpmahjong.net/read.php/541.htm

Theories regarding kabe and suji have already been covered, next will be a summarization of the different degree of safety of tiles, making it into a risk table.

The risk ordering above, should be memorized by beginners, because the ordering above decides what tile to discard first when in betaori, which heavily affects deal-in rate.

Risk factors
The table above refers to normal situations, you should consider the following in a real game:
1) dora
As there will be more points from waiting on the dora, waits on the dora can be predicted. When the dora is chunchan, the deal-in rate is 1.5-1.6 times of the normal rate, while when the dora is a yaochuhai, the deal-in rate increases to 1.8-1.9 times. Also, the tiles near the dora (a.k.a dora soba) have a 10% increase in deal-in rate.
Hence, the degree of safety of the dora tile, yaochuhai's grade has to drop 3 grades, chunchan has to drop 2 grades. While the dora soba has to drop 1 grade.

2) One chance tiles
The degree of safety for one chance tiles is roughly between non suji-pai and suji-pai.

3) The outer tiles of early discarding of 28,37
If the attacker discarded 28, 37 number tiles early, the outer tiles will be safer than usual. (For example if the player who declared riichi discarded 8 sou, then 9 sou is relatively safe.) Deal-in rate is 30% lower than usual.

Also, there are many discard reading books about ura suji, aida yon ken, matagi suji on the market. You might be wondering, why hasn't there been any talk about discard reading.
The reason is because according to game record statistics from 東風莊's super high level tables, this so called discard reading, do not affect the risk of related tiles. So when you're in betaori, it's better to ignore these "skills".


  1. Hello,
    I'am a French fan of Japanese Mahjong.
    I just found your blog, it's really interesting.
    My knowledge of English is not very good and I am having problems for some phrases you use.
    Here are some questions that I ask myself:
    1) For example, for me suji consists of two tiles that make up the ryanmen's attend.
    What is suji-pai? Is it just one of those two tiles or is it the same thing in your mind?
    2) In the table of risks you mention:
    A + suji pai-19
    D non suji-pai 1 and 9
    How can I determine whether 1 or 9 is suji-pai-or non suji-pait?
    3) You also talk
    Double-suji-pai 456
    Half-suji-pai 456
    And non suji-pai 456
    Could you give me a simple example for these three cases?
    Thank you

    Note: Sorry for my poor English

    1. Hi, glaude1955.
      1) You're right. A suji tile is a tile that completes a ryanmen wait.
      2) For a 1 or 9 tile to be a suji-pai, your opponent has to have discarded 4 or 6. Any other time, your 19 tiles are not suji-pai.
      Double suji-pai:
      4 is a double suji-pai when 1 and 7 were discarded.
      5 is a double suji-pai when 2 and 8 were discarded.
      6 is a double suji-pai when 3 and 9 were discarded.
      Half suji-pai:
      4 is a half suji-pai when 1 or 7 was discarded.
      5 is a half suji-pai when 2 or 8 was discarded.
      6 is a half suji-pai when 3 or 9 was discarded.
      Not a suji-pai:
      4 is not a suji-pai when neither 1 nor 7 is discarded.
      5 is not a suji-pai when neither 2 nor 8 is discarded.
      6 is not a suji-pai when neither 3 nor 9 is discarded.
      I hope I helped. :)

  2. Thank you for your answers, it's much clearer to me now.

  3. Hello, i have difficulty to translate "a word tile"
    What do you mean ?

    1. I am sorry about that. I used the term "word tile" since the original author used 字牌. Normally, it's referred to as "honor tile". It's your wind(Ton, Nan, Sha, Pei) and dragon tiles(Chun, Haku, Hatsu).

  4. The game is far more widespread in Asia than in the West. For instance, in 2010 mahjong was the most common table game in Japan, with millions of people playing the game. mahjong game