Riichi Mahjong · Closed 3 / open 2

Honitsu (Half Flush) in Riichi Mahjong: Han, Examples and Odds

In riichi mahjong, Honitsu (half flush) is worth 3 han closed and 2 han open: the whole hand, called sets included, is one suit (characters, dots or bamboo) plus honor tiles. Honors can only be ponned, never chi'd, so honitsu goes hand in hand with yakuhai — it's the most common way to build a big open hand.

The rules for Honitsu

• One suit only among the number tiles: all characters, all dots or all bamboo
• Honors are required; with no honors it's chinitsu
• Chi, pon and kan are allowed, but calling drops it one han (2 han)
• Seven pairs works too: seven pairs from one suit plus honors is honitsu + chiitoitsu

Honitsu vs Chinitsu

Honitsu and chinitsu never stack. One honor pair "drops" a chinitsu to honitsu, but in exchange the seven honors are available, which makes honitsu much easier to build.

How Honitsu is scored

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

Common combinations:

How it relates to other yaku

• Chinitsu: drop the honors and it's chinitsu, 6 han closed. When your hand ends up all one suit, consider switching.
• Yakuhai: honitsu's honor triplets are often dragons or your seat or round wind — pon one for an extra han and a guaranteed yaku when open.
• Toitoi: honors can only be ponned, so honitsu hands often turn into toitoi as well.
• Ittsu, shousangen, chanta: all frequent partners of honitsu.
• Ryuuiisou: 2-3-4-6-8 bamboo plus green dragon — a yakuman shaped like honitsu.

Honitsu odds

How many suit-plus-honor tiles you start with

For honitsu, what matters is "your strongest suit plus all your honors". In a 13-tile start that number is 10 or more about 6.8% of the time, and 11 or more 1.3%.

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

When the four computers on this site play normally, honitsu is in 0.76% of wins, those wins average 8,300 points, and 95% of them were open hands.

Is it worth forcing Honitsu?

We let computers play on this site's table: in every hand, the player with the most tiles of one suit plus honors had to go for honitsu — discard the other suits first, chi and pon that suit and honors, no riichi, and no win without honitsu (or chinitsu) — while the other three played normally. Then we compared the average result with the same starting hands played normally.

Source: computer play on this site. In each of 24,000 hands the seat with the best start forced Honitsu (no riichi, no other win); the other three played normally at normal level. Points are the hand’s gain or loss, including riichi sticks.

The result is clear: from 10 suit-plus-honor tiles, forcing honitsu beats normal play, and the gap grows with every extra tile; in the groups with 9 or fewer, forcing it loses (see the table).

• With 10 or more suit-plus-honor tiles, forcing it works about 26% of the time, for an average of +959; the same starts played normally average +342.
• With 11 or more, the success rate is 33% and the average +1,851, against +511 for normal play.
• Finished hands averaged 3.9 han and 8,300 points, after 13.0 discards.

Which hands suit Honitsu

• Lots of one suit plus honors: see the numbers above.
• A yakuhai pair: pon it and an open honitsu has a yaku, plus one more han.
• That suit connects: with the same count, more partial sets is faster.
• Others will read it: no tiles of that suit in your discards plus a called honor, and they'll hold that suit.

When to give up: someone declares riichi and you're still far, or your suit just won't come. To try it yourself, open a table of free online riichi mahjong — the computers play with you and count the points for you.

Half flush in other mahjong styles

One suit plus honors exists almost everywhere, but scores differently:

• Taiwanese mahjong: 4 tai (Taiwanese mahjong tai list)
• Hong Kong mahjong: 3 fan (Hong Kong mahjong fan table)
• Chinese Official (Guobiao) "Half Flush": 6 fan (Guobiao fan list)
• Sichuan mahjong has no honors, so there's no honitsu — only full flush.

FAQ

How many han is Honitsu?

3 han closed and 2 han open (kuisagari).

Does Honitsu need honor tiles?

Yes. Without honors it's chinitsu, 6 han closed. Only one of them counts.

How many han is honitsu with yakuhai?

An open honitsu with one yakuhai triplet is 3 han; closed adds one more. Add a second yakuhai or toitoi and it's mangan fast.

Related yaku

Chinitsu Closed 6 / open 5 Every tile from one suit — 6 han closed, 5 open. Examples, chinitsu vs honitsu, and how many suited tiles you need. 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. Toitoi Closed 2 / open 2 Four triplets and a pair, still 2 han when open. Examples, scoring combos and how many starting pairs you need.