What Would You Discard?
Riichi mahjong tile-efficiency drills: from a 14-tile hand, pick the discard that keeps the widest acceptance (ukeire). Answers are computed deterministically.
By shanten
Latest problems
🚩 What to Discard: First Steps
New to what-to-discard? Work through these 12 in order — six tenpai (ready) hands, then six 1-shanten. Pick the most efficient discard; solved ones get a ✓.
First Steps →⏱ What-to-Discard Speed Run
How many can you nail in 90 seconds? Pick the widest discard, fast. No hints — your best score is saved on this device.
🖨 What-to-Discard Worksheets (PDF)
Generate free printable what-to-discard (tile efficiency) problems as PDF — for study groups or screen-free practice. Answers (best discard + acceptance) go on a separate page.
Print worksheets →📖 Related reading
- What to Discard: Five-Block Theory and Spotting Useless TilesBefore you count tile acceptance, decide which blocks to keep — the five-block framework. Block strength order and the discard order for isolated tiles.
- Riichi Mahjong Efficiency: The Basics of "What to Discard"How to think about nani-kiru (what-to-discard) problems: shanten, tile acceptance (ukeire), and why pure efficiency is the right default for beginners.
How to play & strategy
What this drill asks
You hold fourteen tiles and must discard one. Choose the discard that keeps your hand’s “acceptance” (ukeire) as wide as possible — that is, the most tiles that move you closer to a finished hand. The answer is computed exactly, so there is always one widest-acceptance discard.
Shanten and tenpai
Shanten counts how many useful draws you are away from tenpai (a ready hand that is one tile from winning). The best discard almost always keeps you at the lowest shanten while leaving the widest set of tiles that advance the hand.
Counting acceptance
Acceptance is every tile type that improves your hand, weighted by how many of each still remain (four of each, minus what you can see). A discard that keeps more useful types usually beats one that keeps fewer; once you reach tenpai, the same idea applies to your winning tiles — a wider wait completes more often.
Efficiency only
These problems isolate pure tile efficiency (牌効率): they ignore yaku, dora, safety, and score. It is the foundation skill — once your shape sense is fast, the situational decisions in a real game become far easier.
What is ukeire (acceptance)?
The set of tiles that improve your hand toward tenpai or a win, counted by how many of each remain unseen. Wider acceptance means your hand completes faster on average.
Why ignore yaku and safety?
This drill trains the base layer of mahjong skill — efficient shapes. Mastering it makes the higher-level decisions about value and defence much more manageable.