Fu 「符」 (pronounced as foo) is a component of scoring. It takes the hand composition into consideration in terms of tile groups, wait patterns and/or win method. In addition, every hand begins with a default start value of 20 fu. To determine the final number of fu, the sources of fu are added up along with the base number and then rounded up to the nearest 10. One exception falls on the yaku chiitoitsu, which is defined and set at 25 fu, regardless of other factors.
For shuntsu (sequences), the fu count is 0. For koutsu (triplet) and kantsu (four-of-a-kind), the fu value depends on whether they are tanyaohai (simples) or jihai/routouhai (honor/terminals).
|Open triplet||Minkou||2 fu||4 fu|
|Open kan||Minkan||8 fu||16 fu|
|Closed triplet||Ankou||4 fu||8 fu|
|Closed kan||Ankan||16 fu||32 fu|
The different basic wait patterns count for fu as well. Combination wait patterns are not listed, such as nobetan, sanmentan, and ryanmenten. Both nobetan and sanmentan counts for tanki; and ryanmenten counts for ryanmen. Other combination patterns factor fu the same as the basic patterns listed here. However, the fu counts only one time. For example, a combination of tanki and kanchan only generates 2 fu from one pattern but not for both.
|Open wait||Ryanmen||0 fu|
|Closed wait||Kanchan||2 fu|
|Edge wait||Penchan||2 fu|
|Pair wait||Tanki||2 fu|
If the hand's pair is of tiles that would score yakuhai in a koutsu, then this scores 2 fu. If the pair doubles up as both the round wind and the seat wind, it may score 2 fu, or 4 fu. That is dependent on which scoring rule is used for this case.
- Winning with a closed hand by ron, the hand is awarded 10 fu. These 10 fu are called menzen-kafu and do not count against the player for achieving pinfu.
- A win by tsumo with an open or closed hand is worth 2 fu.
- An exception to the fu for tsumo is a closed hand that satisfies all other criteria for pinfu. Such a hand does not score 2 fu for tsumo and instead gains the han for pinfu.
- Depending on the scoring rules used, a hand won with a kan replacement tile may also be ineligible for the 2 fu for tsumo, instead scoring only the han for rinshan kaihou.
- An open hand won by ron without any fu from koutsu or the waiting pattern (i.e. 20 fu) is forced to 30 fu. This is often described as being worth 2 fu for an open pinfu.
A hand with 1 han and 110 fu is an exceptionally rare hand. Its requirements are particularly limited, because the hand must be composed of all, not just some, the conditions in the following example.
Example of a 1 han and 110 fu hand:
South player at South round:
- 1 han from yakuhai
- base fu: 20
- closed hand ron: 10
- composition of hand:
Total 102, round up to 110
This is the greatest fu count for any hand worth 1 han, and is only attainable if double winds score 4 fu. If the hand is won by tsumo, then sanankou and mentsumo will be scored; if the triplet of east is closed, then sanankou will still be scored. Finally, the last group must be a sequence, or toitoi would be scored. In these cases, this would add han to the hand.
A hand with 2 han and 110 fu is also possible, as in the following for the East player in the East round:
- 2 han from sanktansu
- base fu: 20
- tsumo: 2
- pair wait: 2
- composition of hand:
Total 108, round up to 110
This is the greatest fu count for any hand worth 2 han. The third quad means that sankantsu must be the only yaku, but one must still be open in order to avoid sanankou. Unlike the 1 han 110 fu example, there is a little bit of leeway: for instance, the hand could be completed on a ron without a double wind pair and still score 110 fu.
With the mangan limit applied, counting this many fu for anything 3 han or higher is no longer relevant, because any han with 70 fu or more is capped at mangan. If the aotenjou scoring system is used however, high fu counts remain relevant towards point calculation.
Technically, pinfu cannot be a yaku while open. However, some open hands produce 0 fu based on composition alone.
This is an open "yakuless" hand. When closed, it resembles that of pinfu. Counting the fu from this hand, it produces 0 fu other than the base 20 fu for every hand. A hand like this can still gain yaku worth 1-han from either chankan, haitei, or houtei. As far as hands go, this pattern generates an exception to the rule behind counting fu; and as a special case, it is granted 2 fu in order to be rounded up to 30 fu.
- Fu in Japanese Wikipedia