One-Shanten Discard

One-shanten means shanten 1. One draw of an ukeire tile reaches tenpai, which this site prints as shanten 0. The win is the next step, printed as −1. On 14 tiles this site sorts cuts by lower shanten, then more ukeire copies, then more ukeire kinds. A gap of one or two copies changes the cut. Scoring, safety, and a missing suit sit beside that ladder and change with the ruleset. This site does not run an expected-value engine.

The frame is tile efficiency. The count is Counting Effective Tiles. The distance is How to Count Shanten. A deficiency count that reads 0 on a finished 14-tile hand sits one away from the integer printed here. The tiles that move the hand one step are the same idea.

Ukeire here is the set of kinds that drop this hand from 1 to 0, plus the copies still left of those kinds. The subtraction is the hand alone: four minus the copies already held. Discards, calls, and indicators stay out. Every figure below is that hand-only count, unless a sentence says it is a side calculation.

What one-shanten is

The name only fixes the distance. Two one-shanten hands can differ by a handful of kinds or by something near a dozen. The narrow end is a working shape plus a tile that adds no kind. 立直 classrooms call that a surplus form (余剰牌形). The count is shared. The Japanese name is the label.

Two man melds, a pair of East, ryanmen 45p, ryanmen 67s, and a spare 9s. A draw of 3p, 6p, 5s, or 8s reaches tenpai. Sixteen copies is a common 立直 classroom line for a count already worth taking, and it is still the narrow member of the set below: 20, then 28, then 36.

Acceptance usually shrinks as shanten falls, so one-shanten into tenpai is the narrow step on an average hand. Arriving with the blocks already chosen is why five-block theory exists.

Wide and narrow

Wide versus narrow is a measured gap in copies at the same shanten. These four hands line up 16, 20, 28, 36. 立直 teaching often ranks the classes the same way: sticky, then headless, then perfect, then surplus. These four happen to line up. The analyzer returns numbers and tile ids. On other deals the middle counts swap.

A perfect shape, with no spare

A perfect one-shanten (完全一向聴), in that 立直 vocabulary, is a pair plus two flexible completions. Every accept reaches tenpai. The count sits in the middle of this set.

Melds 789m and 123s, pair 22p, ryanmen 45p, and 667s. The 66 and the 67 both use 6s, and the list still has 6s once, at ×2 because two copies are already held. Every accepting kind finishes a block or upgrades a pair.

Headless, with a concealed triplet

A headless one-shanten (ヘッドレス) has melds and taatsu, and no pair yet. Completing a taatsu drops shanten. Pairing a tile inside a taatsu drops shanten too. A concealed triplet is why a 立直 reading expects a ryanmen wait more often than a tanki. This page does not grade each accept. The shapes are in Wait Types.

Triplet 222m, melds 456m and 789m, ryanmen 34p, ryanmen 67s. 3m keeps shanten at 1 and raises the kind count from 8 to 9. It stays off the 28. The two lists stay separate.

Side calculation, outside the analyzer. The hand holds no 2p. If all four 2p are already visible, 28 becomes 24. If two are visible, 28 becomes 26. Unseen copies can sit in other hands or the dead wall, so the visible count is an upper bound. The caption stays at the hand-only 28.

Sticky floaters, the wide raw count

A sticky one-shanten (くっつき) is three melds, a pair, and two floaters. The floaters and the pair-to-triplet step make the raw count the widest of these four. Many accepts are poor waits. Near 30 copies, a 立直 reading compares good waits instead of a one-copy gap. Floater strength in that reading runs 3–7, then 2 and 8, then 1 and 9. The analyzer applies no such filter.

Three man melds, pair 55p, floaters 7p and 4s. Different suits, so no shared kind is counted twice. 5p is ×2 because the pair is already held. Both floaters sit in the 3–7 band. That preference sits on top of the 36.

Fourteen tiles: shanten, then copies

Draw to 14, then cut one. Each row is the shanten and the ukeire of the 13 that remain. Lower shanten wins. At the same shanten, more copies win, then more kinds. The whole tie group stays.

Three runs of five, plus an isolated 9s. Each 23456 is a cluster of blocks. The 9s is the tile outside them. Cutting 2m looks like an edge and gives up 26 copies, 46 against 20, at the same shanten.

46 against 20 is the same-shanten comparison. 63 against 46 is shanten first. The 17-copy row is the middle of the run, narrower again.

A man-only count sees seven man kinds, 23 copies. The full list is 14 kinds and 46. The man-flush drill never deals this mixed hand.

When the numbers tie

On that same 14, four cuts match one another on every key. They are the second rank. 9s is strictly better. Among themselves they are shanten 1, 20 copies, 6 kinds. That equality is what you meet whenever the top group has more than one tile. The choice that remains is Discard Strategy.

The other two members of the tie, measured on the same 14:

The sets differ and the totals match, kinds included, so the ladder stops. A sanshoku on 234, a pinfu preference, or a safe tile among the four is 立直 judgment after that stop. The drill would accept every equal-copy cut and ignore kinds. Here the kinds match, so that missing key changes nothing.

Scoring overlays

The ladder does not score tanyao, pinfu, dora, a minimum fan, or a missing suit. Those readings sit next to the structural printout, named by ruleset. A dora, a red five, riichi, or ippatsu can pull a hand off the widest line. This page has no fixed "give up two copies for a dora" amount.

An isolated 1 or 9 connects in two directions, a 2 or 8 in three, a 3 through 7 in four. An isolated honor connects by becoming a pair. That geometry belongs to any ruleset that builds sequences. Tanyao is a separate idea: the hand and the wait both stay inside 2–8.

立直: clearing a terminal can be the widest cut

立直. Tanyao wants every tile, including the wait, inside 2–8. Cutting the last terminal sometimes costs ukeire. On this hand it is the widest cut, and the structural list still contains draws that put a terminal back.

The sort and "remove the only terminal" agree. On this hand, tanyao is the widest line.

Eight of those 43 copies are the two terminal kinds. The follow-up deals play those two draws and no others. The rest of the 43 were not each played out to a tenpai, so this page does not claim that only these eight copies leave the tanyao region.

The ladder's tenpai keeps 1m. A tanyao plan skips that draw even though 1m is structural ukeire of the all-simples 13. Cutting 1m walks back to the 43-copy one-shanten.

The 9m draw does the same thing: the tenpai waits on 8m and still holds 9m. 立直 pinfu is the other common overlay: closed, all sequences, a ryanmen, a valueless pair. When two cuts tie, that reading compares the ryanmen, then the score. On the wall hand below, the ryanmen tenpai is immediate, and the ladder and pinfu agree. There is no fixed number of copies to give up for it.

国标: the structural tenpai can wait in another suit

国标. The structural list is every kind that lowers shanten. 实质进张 is the subset that advances the core fan. 改良进张, in association teaching, leaves the distance unchanged and widens the wait. This site lists an improvement only when the kind count rises. 型听 is structural tenpai under the minimum fan. This page does not compute that fan, so a caption can say the wait is off a named plan, and it gives no fan total.

断幺 asks for the opposite of 带幺九 or 全带幺. A 立直 habit of cutting terminals is the wrong default on a 全带幺 plan. Name the fan. Chi exists here. The pair-times-four and sequence-times-two equivalent on the ukeire page is not this copy total, and 川麻 has no chi to apply it to.

The ladder takes a ryanmen in pin. The bulk is sou, and a pin is still held. For a sou-flush plan, 实质进张 is a different question from 1p and 4p. The minimum fan for that pin wait is unknown here.

The 43-copy row is still one-shanten, and it still holds 3p. The structural best cut and the one-suit plan are different questions. See Chinese Official Mahjong.

川麻: the missing suit, then the two-suit count

川麻. House rules differ. This reading follows 血战到底-style play: the deal can continue after a win, the set is 108 tiles with no honors, there is no chi, and 定缺 clears one suit before a win is legal. A structural tenpai whose only wait is that missing suit is not a legal hu.

The ladder already cuts a man. Under 定缺 of man, the table rule agrees. Cutting a pin or a sou instead leaves shanten 1 and 33 copies, with a man still in the hand.

Cutting 2m leaves the mirror: shanten 0, 1m×3, with 1m still in the hand.

After 定缺 of man is clear, two suits remain. Sequence accepts stay at their hand-only copies. There is no chi.

Two live suits, hand-only copies, legal tiles only. During the hand the sort still prefers lower shanten. At an exhaustive draw, 查叫 compares tenpai with noten, so a narrow legal tenpai beats a wide one-shanten when the wall is ending. On a continuing 血战到底 deal that narrow tenpai can remain the goal after someone else has won. See Sichuan Mahjong. 川麻 danger is dealing in, the missing suit, and 查叫. This sidebar does not use the word genbutsu.

Seven pairs, only where that win exists

Count seven pairs only on tables that include that win. 立直 includes it. 国标 includes it as a special pattern. 川麻 scores it on some 血战到底 tables and omits it on others. These hands are seven pairs, not thirteen orphans. The integers include seven pairs. A table that omits the pattern needs a different distance, and this page does not print that other number.

Four one-shanten cuts tie at 9 copies. Breaking a pair is shanten 2 with 15. The larger count loses the first key.

Genbutsu, safety, and the wall

A safe cut can cost sixteen copies

立直. Genbutsu is a tile already in one player's discard row, or a tile that passed after their riichi. It rules out every wait against that one player. A second riichi is a separate question. Furiten is why a wait you discarded is dead against you. Riichi freezes the hand, so later shape changes stop. See Riichi Mahjong.

The ladder does not know genbutsu. Folding to a genbutsu tile is a 立直 override of the sort. 国标 and 川麻 do not inherit riichi furiten. 国标 danger is that ruleset's calling and scoring. No deal-in percentage is printed here.

Pair 55p, floater 3s, West, and Red Dragon, beside a finished man suit. The two honors match on every key.

Cutting Red Dragon leaves the same pins and sous, with West×3 in place of Red Dragon×3.

If 3s is genbutsu against one riichi and the honors are live, folding to 3s stays at one-shanten and the count falls from 24 to 8. Against a second riichi, 3s can still deal in. The ladder's best cuts remain the two honors.

A tie makes the safe cut free

立直 for the safety sentence. The tie itself is the shared ladder. The surplus hand, plus a South, has two spare tiles.

If South is genbutsu and 9s is live, the safe cut costs zero copies. On the previous hand the safe 3s cost 16. The accept set matches either way. The improvement list does not: cutting 9s leaves a 13 that can still widen, and cutting South leaves the empty list.

Cutting East falls to shanten 2 with 28 copies. Cutting 4p or 5p falls to shanten 2 with 45. Cutting 6s stays at one-shanten and narrows 16 to 12: the 67s ryanmen becomes a 79s kanchan waiting on 8s. Same shanten, fewer copies.

A thin wall: tenpai with 8 beats one-shanten with 36

A small tenpai beats a wide one-shanten, because the second hand still needs two successful draws. Late in the hand that is obvious. The ladder says it from the first cut. Refusing the tenpai to widen the shape later is early-game 立直 judgment. The ladder will not make that choice, and the drill will not either.

A 立直 pinfu reading takes 3p as well: closed, all sequences, ryanmen, valueless pair of 2p. Eight copies is a small tenpai. It outranks 36.

Keeping this 13 means refusing the tenpai. That is the early-game judgment above. It is outside the sort.

Cutting 2p leaves the headless 13: shanten 1, eight kinds, 28 copies, with no improvement rows. It loses to the tenpai on shanten and to the 36-copy line on copies.

An improvement draw stays at one-shanten

Ukeire lowers shanten. An improvement draw does not. This site lists one only when shanten stays the same and the kind count rises. A draw that adds copies and no new kind is invisible. A draw that only sweetens a future wait, with no new kind, is invisible. Tenpai has an empty list. The 国标 name 改良进张 stays in that section. The mechanism here is shared.

The sticky 13 has no extra 3m. Drawing 3m keeps shanten at 1 and moves the kind count from 10 to 14 on the hand that now holds it. 3m is not ukeire of the old 13. The question is which tile you cut after the draw.

The sort already wants 7p. Throwing the 3m you just drew walks back to 36.

The new tile stayed. The discard was 7p. Thirty-six copies and 10 kinds became 47 copies and 15 kinds, still at shanten 1. Cutting 4s is the middle: shanten 1, 43 copies, 14 kinds.

Cutting 1m or 2m is shanten 2 with 71 copies. The larger count loses.

Drills at 8, 11, and 14

The discard drill is one-shanten discard. Thirty seconds, lengths 8, 11, and 14, man flush only. One-shanten training is the other route: name the accepting kinds on 7, 10, or 13 tiles. That route lines up with the ukeire page.

Each deal starts as a one-shanten man hand one tile short, then adds one man that is not already an accepting tile. The ladder still takes lower shanten, then more copies, then more kinds. The green tiles are the cuts that stay at shanten 1 and tie for the most man-only copies. A tenpai cut scores 0. Kind count is not a drill tie-break. The two rules meet only when the widest cut is already one-shanten.

The analyzer scores 13 tiles as a hand and 14 tiles as a cut. After an 8-tile cut, seven mans remain and the distance pretends an East triplet and a South triplet are finished. After an 11-tile cut, ten mans remain plus one East triplet. The screen shows only the mans. 川麻 has no honors, so this fragment is not a 川麻 deal, and a 国标 hand does not invent triplets that were never dealt. The pictures add those stand-ins so the 13-tile view matches the drill. Every accepting kind here is a man, so the man-only count and the full list match.

Eight tiles

The visible deal is m12346689. Eight mans.

The ladder takes 1m or 4m. The drill's green tiles are 8m and 9m.

Inside that one-shanten band, cutting 6m scores 23, cutting 2m scores 12, and cutting 3m scores 8. The tenpai cuts score 0 in the drill and win on the ladder. At 14 tiles the analyzer's cut table is that ladder, with no stand-in honors. A tenpai cut is still never the green tile.

Eleven tiles

The visible deal is m12345677889. Eleven mans. After the cut, the distance pretends one East triplet.

Same split at the middle length. The ladder's best cuts are tenpai with 8 copies. The green tiles are 3m and 6m. On both sample deals the tied cuts also match on kinds, so the drill's missing kind-count key changes nothing inside the tie. The disagreement is tenpai against one-shanten.

What to practice

The ladder's best cut is the efficiency best cut. A scoring plan, a missing suit, or an exhaustive-draw tenpai is an overlay you name before you play past the numbers.

1. The distance, including 0 and −1, in How to Count Shanten.
2. Kinds and hand-only copies, in Counting Effective Tiles. Name the kinds in one-shanten training.
3. The cut at shanten 1, on this page. The isolated tile, when five blocks are already chosen, is in five-block theory.
4. A tie on shanten, copies, and kinds, in Discard Strategy. Good-wait comparisons live there once the sort has stopped.
5. The wait as a shape, in Wait Types. At tenpai, ukeire and the wait are the same set.
6. The table. Riichi Mahjong, Chinese Official Mahjong, or Sichuan Mahjong. A 立直, 国标, or 川麻 sentence travels only into the ruleset it names.