<aside class="article-notice"><b>Rewritten 2026-09-04.</b> An earlier version of this article used the Japanese pair <i>ukeire / shanten</i>. American mahjong does not use those terms: the answers to "how far" and "how many tiles improve me" come from the card, not from a shanten count. This version works directly from the 2026 NMJL card and the tiles still alive.</aside>
<h2>The two questions every discard is answering</h2>
Every discard you ever make is the answer to two questions:
<ol> <li><b>How far am I?</b> How many tiles away from a complete hand.</li> <li><b>How many tiles improve me?</b> How many tiles in the remaining wall would advance me.</li> </ol>
In Japanese mahjong these have names, <i>shanten</i> for the first, <i>ukeire</i> for the second, and an enormous technical literature. The American game needs the same two answers but gets almost none of the vocabulary, which is a shame, because the American version is easier.
<h2>How far am I? (the American version)</h2>
Look at the row you are playing from the card. Count the groups the row needs. Subtract the groups you have already made. Subtract half-pairs if you have them. The remainder is how many tiles you still need.
<ul> <li>If your card line needs five groups and you have four complete plus a pair, you are <b>one tile away</b>.</li> <li>If you have three complete and two half-built, you are <b>two tiles away</b>.</li> <li>If you have two complete and two half-built and one loose tile, you are <b>further than that</b>.</li> </ul>
Further is worth counting precisely because it is usually worse than it looks. A hand that needs four more tiles on a single row has effectively no chance of finishing before the wall runs out.
<h2>How many tiles improve me? (the American version)</h2>
For each tile you still need, count how many of the four copies are still unseen. Add the numbers together. That is your tile availability.
Examples:
<ul> <li>You need three more 7-dots. The discards and exposures show 7-dot, 7-dot, 7-dot. The fourth is the only unseen copy, and jokers can substitute for it. You have 1 + 2 jokers live, so 3 tiles can complete the pung.</li> <li>You need a pair of winds. The discards show one East, one South. The other East and South are unseen. You have 2 tiles live.</li> </ul>
When your tile availability is small (say, two or three total live tiles), the row you are playing is fragile. A swap or a switch to a backup row is often the right call.
<h2>What the card gives you that the tiles do not</h2>
The 2026 NMJL card lists every legal hand. Most rows on the card overlap on the same tiles: the same 5-dot appears in four or five different rows. This means tile availability is rarely as small as it feels. A 5-dot you think is dead for your row may be live for someone else's.
Two habits keep you oriented. First, <b>know your backup row</b>. Before you commit to a single row, have a second row in mind that uses the same broad family. Second, <b>keep a one in the rack</b>. If you have only one tile of a vital family left, do not throw it; the wall is finite and you will likely need it back.
<h2>Joker modifiers</h2>
A joker can substitute for any tile in a three-or-more group. It cannot substitute for a single or a pair. So a quint of five identical tiles needs four real tiles plus one joker (the joker is the fifth); a sextet of six needs two jokers. The joker count matters more in American mahjong than the Japanese game because the hands are larger.
Add jokers to your tile availability only for groups that take jokers on the card. Most Concealed rows take no jokers; their tile availability is just the real tiles unseen.
<h2>When to switch</h2>
Switch rows when your tile availability drops below what a reasonable row requires (typically three or four live tiles). Switch entirely when two of your backup rows are also dead. A dead row is one whose key tiles are all visible.
Remember: in American mahjong, switching rows after exposing is not allowed: the row locks at the first exposure. So the decision to switch must be made <i>before</i> you expose. This is the highest-value discard decision in the game.
<h2>Further reading</h2>
The card-reading guide is on the Card page, and the defense reading guide is on the Defense page. The full hand-by-hand layout is on the Card library. The 2026 NMJL card is the final authority.
<hr><small>The prior ukeire / shanten version of this article is retained in our archive for reference only.</small>