What is Ippatsu?
Ippatsu (one-shot) is an incidental yaku that awards 1 han for winning within one turn after declaring riichi. Named “one-shot” for the immediate win, it’s luck-based but surprisingly common, adding to riichi’s appeal.
Learn it together with riichi - riichi + ippatsu + tsumo makes 3 han, and with ura-dora, it can quickly become a high-scoring hand.
Conditions
| Condition | Description |
|---|---|
| After riichi | Must have declared riichi |
| Within 1 turn | Before your next draw |
| Win | Tsumo or ron both work |
Counting One Turn
One turn = from your riichi declaration until your next draw
You (Riichi) → Shimocha → Toimen → Kamicha → You (end of 1 turn)When Ippatsu Is Cancelled
The following actions cancel ippatsu:
| Action | Description | Example |
|---|---|---|
| Calls | Anyone’s pon/chi/kan | Cancelled the moment someone calls |
| 1 turn passes | Your 2nd draw | No ippatsu on 2nd draw |
Probability
| Situation | Rate | Notes |
|---|---|---|
| Ippatsu tsumo | ~10% | With good shape wait |
| Ippatsu ron | ~15% | Depends on opponents’ discards |
| Total ippatsu | ~20-25% | Tsumo + ron combined |
Wait Shape and Ippatsu Rate
| Wait Shape | Ippatsu Rate | Reason |
|---|---|---|
| Multi-wait | High | More winning tiles |
| Ryanmen | Normal | Standard probability |
| Bad shape | Low | Fewer winning tiles |
Strategy for Aiming Ippatsu
Riichi Timing
-
Early riichi
- Fewer opponent calls
- Higher ippatsu chance
-
Good shape riichi
- Easier to win
- Higher ippatsu rate
-
Chasing riichi can still get ippatsu
- After opponent’s riichi
- Counts from your riichi
Ippatsu-Cancelling Strategy
From defender’s perspective:
- Intentionally call to cancel ippatsu
- Lowers opponent’s score
- Especially effective vs parent riichi
Ippatsu and Other Yaku
Always Combines With
| Yaku | Reason | Minimum Han |
|---|---|---|
| Riichi | Prerequisite | 2 han (riichi + ippatsu) |
Common Combinations
| Yaku | Pattern | Expected Han |
|---|---|---|
| Tsumo | Ippatsu tsumo | 3 han |
| Pinfu | Riichi-ippatsu-pinfu | 3 han |
| Tanyao | Riichi-ippatsu-tanyao | 3 han |
| Ura-dora | Luck-based | 3 han+ |
Ippatsu Value
Basic patterns:
- Riichi only → 1 han
- Riichi + Ippatsu → 2 han (×2)
- Riichi + Ippatsu + Tsumo → 3 han (×4)
Common Mistakes
-
Doesn’t work without riichi
- Damaten instant win isn’t ippatsu
- Riichi required
-
Cancelled by calls
- Your own calls = can’t riichi anyway
- Others’ calls cancel ippatsu
-
Ankan also cancels
- Anyone’s ankan cancels ippatsu
- Any kan type cancels it
-
2nd turn isn’t ippatsu
- No ippatsu on your 2nd draw
- Understand the 1-turn definition
Practical Tips
Ippatsu-Conscious Play
-
Riichi decisions
- Include ippatsu in expected value
- Earlier turns = more favorable
-
Watch for opponents
- Be wary of riichi player’s ippatsu
- Secure safe tiles
-
Calling decisions
- Value of ippatsu cancellation
- Balance with your hand
Psychological Aspects
- Pressure: Fear of ippatsu distorts discards
- Expectation: Riichi player hopes for ippatsu
- Mind games: Timing of ippatsu cancellation
Related Terms
- Riichi: Prerequisite for ippatsu
- Tsumo: Self-draw win
- Ron: Win on discard
- Ura-dora: Riichi bonus
- Menzen: Closed hand state
Summary
Ippatsu is a luck-heavy yaku, but it’s part of mahjong’s charm. Valid only for 1 turn after riichi, it’s cancelled by calls. Beginners should remember “within 1 turn after riichi” and “cancelled by calls.” Considering ippatsu in expected value calculations leads to more strategic riichi decisions.