Riichi Mahjong Efficiency: The Basics of "What to Discard"

"What to discard" (nani-kiru) is the most common puzzle in riichi mahjong: you hold 14 tiles and must choose the one discard that gives your hand the best chance to improve. For beginners, the most valuable habit is to discard for pure efficiency — keeping the tiles that accept the most useful draws.

Shanten: how far from tenpai

Shanten is how many tile swaps you are away from tenpai (a ready hand). A 1-shanten hand needs one good draw to reach tenpai; 2-shanten needs two. The first rule of an efficient discard is never to raise your shanten — keep the hand as close to tenpai as you can unless you have a strong reason not to.

Ukeire: counting your acceptance

Among discards that keep the same shanten, the best one usually accepts the most tiles — this count is called ukeire (tile acceptance). An open two-sided shape such as 4-5 (which accepts both 3 and 6) takes in more than a closed wait like 4-6 (waiting only on 5) or a lone pair. Counting how many tiles each discard accepts, and how many of those are still live, is the heart of efficiency.

• Prefer two-sided (ryanmen) shapes over closed kanchan/penchan waits.
• Keep tiles that connect to more of your hand; drop isolated terminals first.
• Among equal-ukeire choices, weigh tile safety and future hand value.

When to look past pure efficiency

Efficiency is the right default, not the whole game. As you improve you also weigh hand value (yaku and dora), the danger of dealing into an opponent, and how many turns remain. Strong players bend efficiency for value or safety when the situation calls for it — but they always know what the efficient discard was first.

How to practice

Drill many positions and check your answer against the tile acceptance. On TsumeDojo each what-to-discard problem shows the accepted tiles and the count after you answer, so you can see exactly why a discard is best. Solving a lot of these builds the instinct to spot the efficient discard at a glance.