Riichi Mahjong · Closed 2 / open 2

Shousangen (Little Three Dragons) in Riichi Mahjong: Han, Examples and Odds

In riichi mahjong, Shousangen (little three dragons) is worth 2 han: two of the three dragons (white, green, red) as triplets or quads, and the third one as the pair. Calling keeps it at 2 han. Each dragon triplet is also a yakuhai, so a shousangen hand always has at least 4 han.

The rules for Shousangen

• Two dragons as triplets or quads (pon, concealed triplet, open or closed kan all fine)
• The third dragon as the pair
• The other two sets and suits are free; sequences are fine
• 2 han closed or open

If all three dragons are triplets, it isn't shousangen but the daisangen yakuman.

How many han Shousangen really is

The dragon pair gives no han, just 2 fu. Add a little honitsu, toitoi or dora and haneman comes easily.

How Shousangen is scored

The yaku, han, fu and points below are computed live by the same scoring code the game uses.

How it relates to other yaku

• Daisangen: make the pair dragon a triplet as well and it's a yakuman. If your shousangen waits on a shanpon with the third dragon, winning on that dragon turns it into daisangen.
• Yakuhai: the two dragon triplets inside shousangen still each count as yakuhai.
• Honitsu, Toitoi: dragons can only be called by pon, so three honor sets plus one suit is a natural shape, and these two combine often.

Shousangen odds

How many dragon pairs you start with

Shousangen needs at least two of each dragon. In a 13-tile starting hand, two or more dragons are a pair or better about 0.46% of the time; all three only 0.0049%.

Source: 1,000,000 random 13-tile deals.

How often it happens in play

Four normal-level computers played 40,000 hands on this site's table with 33,226 wins; shousangen appeared 2 times (0.0060% of wins). The computers play for speed and rarely wait for the third dragon, so in practice shousangen mostly happens when two dragons get called and a pair of the third just happens to be there.

Which hands suit Shousangen

• Pairs of two dragons and at least one of the third: pon two, keep one as the pair — a clear route.
• Dragons not yet discarded: once two of a dragon are gone, it can only be your pair.
• Others will defend: show two dragon triplets and everyone fears daisangen, so the third dragon almost never comes out. Expect to draw your pair yourself.

To try it, open a table of online riichi mahjong — the computers play with you and count the han for you.

Shousangen in other mahjong styles

• Taiwanese mahjong: little three dragons, 4 tai (Taiwanese mahjong tai list)
• Hong Kong mahjong: little three dragons, 5 fan (Hong Kong mahjong fan table)
• Chinese Official (Guobiao): little three dragons, 64 fan (Guobiao fan list)

FAQ

How many han is Shousangen?

Shousangen itself is 2 han, open or closed. With the yakuhai from its two dragon triplets it's really at least 4 han.

What's the difference between Shousangen and Daisangen?

Shousangen is two dragon triplets plus a dragon pair; daisangen is all three dragons as triplets, a yakuman.

Is Shousangen always mangan?

No. It's at least 4 han, which is mangan at 40 fu or more but not at 30 fu (this game has kiriage mangan off by default).

Related yaku

Daisangen Yakuman Triplets of all three dragons — a yakuman even when called. Examples, pao rules and starting-hand odds. Yakuhai Closed 1 / open 1 A triplet of dragons, seat wind or round wind — 1 han, even when called. Double wind, atozuke and one-sided waits. Honitsu Closed 3 / open 2 One suit plus honors — 3 han closed, 2 open. Examples, honitsu vs chinitsu, and how many tiles you need to go for it.