Japanese mahjong scoring rules

Japanese mahjong features a very complex scoring system. Nearly every mahjong hand has a value in terms of han and fu, which are plugged into an equation to derive the hand's points. Alternatively, a scoring table can be used to find a hand's point value directly.

Generally, a game starts players with 25,000 points, with the goal of scoring at least 30,000 by the end for first place to declare victory. Both of these values can be changed; tournament play in particular often starts with 30,000 points.

Scoring factors

Han

Han 「飜」 is the main portion of scoring. Each yaku is assigned a value in terms of han: most are valued at 1-2, going up to 6 han for closed chinitsu. Some yaku are worth -1 han with an open hand, and others cannot be scored at all with an open hand. Also, each dora in the hand grants +1 han. A hand's yaku and dora are added up to produce a total han value.

Players are encouraged to know yaku, their han values, and how much points a given hand is worth. This knowledge may help with various game decisions, particularly when calling riichi or abandoning the hand.

As a general rule, for every +1 han, the hand roughly doubles in value until reaching 4 han. There is a "cap" at 2000 base points (5 han; 4 han 40+ fu); a hand that scores this much is called a mangan hand. Once reaching mangan, fu no longer matters for points, and han is reduced in value.

Fu

Main article: Fu

Fu 「符」 (pronounced as foo) takes the hand composition into consideration in terms of tile groups, wait patterns and/or win method.

Every hand begins with a default of 20 fu. Any extra sources of fu are added, and then rounded up to the next multiple of 10. The exception is with chiitoitsu yaku, which is fixed to 25 fu (and not rounded).

Fu does not impact scoring for hands that have at least 5 han.

Yakuman

Main article: Yakuman

The highest-scoring combinations are the yakuman patterns. A hand completing a yakuman is not scored for han and fu, but depending on the rules, it may be possible to combine multiple yakuman for an even larger hand.

Scoring procedure

Calculating basic points

To determine the point value of a hand, the following procedure is used:

If the hand is a yakuman, then the hand scores 8,000 basic points.
1. If double yakuman are used, a double yakuman scores 16,000 basic points. If multiple (>2) yakuman are used, points are multiplied accordingly.
Otherwise, determine all of the hand's valid yaku and determine the amount of dora dora. Count the number of han from these sources.
1. Some yaku combinations such as chanta + junchan are not compatible with each other.
If the han count is 5 or more, then counting fu is no longer necessary. The hand is scored according to its han value:
1. 5 han: mangan hand worth 2,000 base points.
2. 6-7 han: haneman hand worth 3,000 base points.
3. 8-10 han: baiman hand worth 4,000 base points.
4. 11-12 han: sanbaiman hand worth 6,000 base points.
If the han count is 4 or less, then count fu.
1. If the hand is not seven pairs, round the fu up to the nearest 10.
To get the base points, plug in the equation fu × 2^{(2 + han)}
If playing with kiriage mangan, round a 1,920-point hand up to a 2,000-point mangan.
In any case, if the base points value would be above 2,000 for a hand with 4 or fewer han, it is instead a 2,000-point mangan.

Payment multipliers

After determining the basic points, multiply based on the status as dealer and no-dealer as well as the win by ron or tsumo.

When a non-dealer wins by tsumo, the player is paid 1 × basic points by the other non-dealers, and 2 × basic points by the dealer.
When a non-dealer wins by ron, the discarding player pays the winner 4 × basic points.
When the dealer goes out by tsumo, the player is paid 2 × basic points from all other players.
When the dealer goes out by ron, the discarding player pays the winner 6 × basic points.

Each value to be paid is rounded up to the nearest 100.

The numbers for a ron payment are obtained by having the ronned player pay every other players points. Because rounding is done after this reassignment of points, it is sometimes the case that a win by tsumo is worth a few hundred more points than a win by ron.

Honba

Main article: Honba

In addition to the points for the hand, the winner is paid a small sum of points based on the number of honba counters on the table. Thus, as a hand is repeated, its value goes up slowly.

Oyakaburi

Oyakaburi 「親かぶり」 is when a non-dealer player wins by tsumo, causing the dealer to pay more than non-dealer players. This term usually refers to high value tsumos, which can cause the dealer to drop down placement.

Scoring Table

Main article: Scoring table

Since the han and fu equation is always the same, it is possible to use a scoring table to score the hand. Simply calculate the hand's han and fu, then find the values on the table. See scoring table for the actual table.

For details on how to memorize scoring, see score table memorization.

End game score

Main article: Final scores

At the end of the game, the raw points are used to calculate the end game score. These are the two or three digit +/- numbers used to reflect a player's score. For example:

A player ends the game with 40,000 points.
The starting value of 25,000 points is subtracted, leaving +15,000 points.
To make the values easier to read, 15,000 is divided by 1,000, for a value of +15.0 points.
This +15 value may be affected by uma (a bonus/penalty for placing 1st/2nd/etc.).

Aotenjou

Main article: Aotenjou

Aotenjou is a rarely played variant which removes the mangan limit. Under aotenjou:

Each han doubles the hand value without limit. E.g., a 5 han 30 fu hand is 8000 in standard rules, and 15360 in aotenjou.
Fu matters even for hands with 5 or more han.
Yakuman are scored as 13-han yaku.

External links

麻雀の得点計算

Japanese mahjong scoring rules in Japanese Wikipedia