Every turn in mahjong ends the same way: you have one tile too many and have to throw one out. This calculator compares every possible discard and shows which one keeps your hand closest to winning, with the most ways to improve. It's a free tool from Mahjong Academy, built on the same hand-reading code as our games.
On this page
How to use it
Build your hand with the tile picker or type it in (m characters, p dots, s bamboo, z honors 1–7). Then:
- With 14 tiles (or 17 in Taiwanese mahjong), it's your turn to discard. You get a table of every discard, best first.
- With 13 tiles (or 16), you're waiting for a draw. You get your shanten number and every tile that would move you forward.
Fewer tiles work too if you've called sets: anything from 1 to 17 tiles, as long as it isn't a multiple of three.
What shanten means
Shanten is a Japanese word for "how many tiles away from ready". A ready hand (tenpai) is 0. A hand that needs one more useful tile before it's ready is 1-shanten, and so on. A complete hand is shown as a winning hand.
The number counts *useful* tiles, not turns. You might draw five useless tiles in a row and still be 1-shanten. That's why the second number, how many tiles help, matters so much.
How to pick a discard
The table sorts discards by two things, in this order:
- Shanten after the discard. Lower is better: always stay as close to ready as you can.
- Tiles that help. Among discards with the same shanten, take the one with more useful draws. 20 tiles beats 12.
Rows marked Best are tied on both. Picking between them is where style comes in: keep the tiles that could make a bigger hand, or let go of the one that's safer against a dangerous opponent. If you're still learning what a set and a pair look like, the sets and pair lesson is a good first stop.
What the numbers can't see
The calculator reads your hand and nothing else, so keep these in mind:
- It doesn't know what's already been discarded. A wait on tiles everyone has thrown away looks better here than it really is.
- It doesn't think about scoring. Sometimes a slower hand worth much more is the better plan.
- It doesn't defend. When someone else looks ready, throwing a safe tile can beat the "best" discard.
Use it to train your eye for shapes, then let your judgement handle the rest.
Frequently asked questions
Is shanten only for Japanese mahjong?
The word comes from Japanese mahjong, but the idea works for any style where you build sets and a pair: Chinese, Taiwanese, Hong Kong and Japanese mahjong all use it, even if players call it something else.
Why does seven pairs change the result?
Seven pairs is a different winning shape. A hand full of pairs can be close to ready as seven pairs while still far from four sets and a pair. Turn it off if your rules don't allow it, such as Taiwanese 16-tile mahjong.
How do I check what a ready hand waits on?
Open the wait calculator with the same hand: it lists every winning tile and how many are left.
When you're ready to use all this in a real game, head back to the Mahjong Academy homepage and pick a style to play for free.