Mahjong Tile Efficiency – Shapes & Ukeire

Mahjong tile efficiency compares routes toward a complete hand. In riichi, the usual order is: reduce shanten first, then compare ukeire—the remaining tiles that improve the hand. The same shape logic helps in other four-groups-and-a-pair variants, although scoring and special-hand rules can change the best discard.

The 3 measurements

Mahjong Tile Efficiency – Shapes & Ukeire: Measure, Question, Use

Measure	Question	Use
Shanten	How many improvements from ready?	Compare overall progress.
Ukeire	Which unseen tiles reduce shanten?	Compare candidate discards at equal distance.
Shape quality	What waits and follow-ups remain?	Break ties and protect future flexibility.

Do not count tile names alone. Count remaining copies. If a shape accepts 2 and 5, but 3 copies of 5 are visible, only 5 live tiles remain: four 2s and one 5.

Read common incomplete shapes

Two-sided shape

3-4 accepts 2 or 5 to complete a sequence. With no visible copies, that is 8 possible tiles. Two-sided shapes are strong because they use 2 ranks and often lead to better waits.

Closed shape

3-5 accepts only 4, normally 4 copies before visible tiles are removed. It is useful but less flexible than a two-sided shape.

Edge shape

1-2 needs 3; 8-9 needs 7. These shapes also have 4 maximum completing copies and cannot expand outward past the end of a suit.

Pair

6-6 accepts the 2 remaining sixes to become a pung, but the pair may already fill the hand’s required pair slot. Its true value depends on the rest of the hand and whether the tile carries value.

Strong multi-tile shapes

Blocks such as 2-3-4-5 do more than contain 1 completed sequence. They can reorganize when nearby tiles arrive and may produce 2 groups or a strong final wait. Do not break a connected block only because another part of the hand looks neatly separated.

Overlapping shapes are why simply circling “complete groups” can be misleading. Before locking tiles into a group, test whether they also support another sequence.

A discard comparison

Imagine the suited block 2-3-5-6-8. Compare discarding 8 with discarding 2.

• After discarding 8, the hand keeps 2-3 and 5-6, 2 two-sided shapes with several improving ranks.
• After discarding 2, the hand keeps 3 isolated beside 5-6-8; fewer connections remain unless the rest of the hand gives 8 a special role.

The first choice is normally more efficient for a standard hand. But if 8 is required for an American card line or supports a valuable special route, the ruleset overrides the generic comparison.

Efficiency has constraints

Value

A riichi hand needs a yaku. Breaking the only value source to gain a few acceptance tiles can create a fast hand that cannot win. In other variants, minimum fan or special card requirements create the same kind of constraint.

Safety

When an opponent shows a major threat, the most efficient discard may be too dangerous. Preserving a safe tile or folding entirely can have higher expected value than maximizing ukeire.

Calls

Open calls may reduce shanten immediately but remove closed-hand value and flexibility. Compare the post-call route, not just the satisfying moment of completing a group.

A 10-minute drill

Deal 13 tiles. Write 2 discard candidates, the shanten after each, and every improving tile. Subtract visible copies. Then add 1 constraint—a yaku requirement, opponent riichi, or score target—and decide again.

Daina Chiba’s free Riichi Book I provides a deeper progression through shapes and efficiency. Use this page as the working checklist: distance first, live acceptance second, value and safety always.