Half Outside Hand

What is Half Outside Hand in Japanese Mahjong

Half Outside Hand is a hand in Japanese Riichi Mahjong that emphasizes terminals (1s and 9s) and/or honor tiles (winds and dragons) in every set and pair, but still allows the inclusion of mid-range suit tiles (2–8) in the hand. Half Outside Hand emphasizes using at least one terminal (1 or 9) or honor tile in every set and pair. It scores 2 han when closed and 1 han when open in standard Riichi rules. Balancing whether to open (and reduce the hand’s han value) or remain concealed (for a bigger reward) is a core strategic consideration. While not as restrictive as Pure Outside Hand or as extreme as All Terminals and Honors, Half Outside Hand still provides a potentially solid scoring route that can combine with other yaku for a rewarding hand.

How to Achieve Half Outside Hand？

Each Set and the Pair Must Contain at Least One Terminal or Honor: A set (triplet/quad or sequence) is valid for Half Outside Hand if it includes at least one 1, 9, or honor tile. For sequences (chows), this practically means they must be 1-2-3 or 7-8-9, since those include a terminal. The pair also must be either a 1, 9, or an honor tile.

“Mixed” Aspect: The term “half outside” indicates that honors can be part of the hand, but not all tiles are terminals/honors exclusively (otherwise it would be All Terminals and Honors). In practice, many of the Half Outside Hand hands do include some mid-range suit tiles (2–8) alongside at least one terminal/honor in each set.

Yaku Value:

• 2 han if the hand is fully concealed
• 1 han if the hand is opened

Hand Structure Examples

• Sequence: 1-2-3 of Man
• Sequence: 7-8-9 of Man
• Triplet: 9 of Sou
• Triplet: East Wind
• Pair: 1 of Dots

Every set and the pair includes a 1, 9, or honor tile, fulfilling the requirement. Because this hand is concealed, it would grant 2 han for Half Outside Hand.

What is the Strategy and Risk of Half Outside Hand?

Open vs. Closed: You may choose to open your hand by calling tiles (chow/pung), which makes it easier to collect the required 1s/9s/honors for each set—but reduces the yaku’s value to 1 han. If you can afford to keep the hand concealed and still complete it, you’ll gain 2 han, which is more lucrative.

Tile Availability: Half Outside Hand often relies on sequences of 1-2-3 or 7-8-9. If many of these terminal tiles are already discarded or appear in opponents’ melds, you might reconsider or switch strategies.

Combining with Other Yaku

• Yakuhai: If your triplets include seat wind, round wind, or dragon tiles, you can gain an extra han for each such set.
• Riichi: If your hand remains fully concealed, you can combine Half Outside Hand with Riichi or Fully Concealed Hands, further boosting your total han.
• Dora: Even if you have mid-range tiles, any dora among them will naturally increase your score.

Warning Opponents: Frequent calls of 1, 9, or honor tiles may alert opponents that you’re pursuing Half Outside Hand or a similar terminal/honor-based yaku. They could become more cautious with discards, especially honor tiles.