Riichi Mahjong · 1 han（closed only）
Ippatsu in Riichi Mahjong: Rules, What Breaks It, and Odds
In riichi mahjong, Ippatsu ("one shot") is worth 1 han: after you declare riichi, you win before your next discard, and nobody has made a chi, pon or kan in between. Only the riichi player can get it, by tsumo or ron.
The rules for Ippatsu
- You must have declared riichi or double riichi
- You win before your next discard: ron on someone's discard, or tsumo on your next draw
- In that time nobody calls chi, pon or kan (that includes your own closed kan and anyone's added kan)
- If your declaring discard is ronned, the riichi doesn't count — and neither does ippatsu
What cancels Ippatsu
| What happens | Ippatsu |
|---|---|
| Anyone calls chi, pon or open kan | Gone |
| Anyone makes a closed or added kan (you too) | Gone |
| You draw, don't win, and discard again | Gone |
| Others just draw, discard or declare riichi | Still on |
How Ippatsu is scored
The yaku, han, fu and points below are computed live by the same scoring code the game uses.
Riichi · Ippatsu · Ron
| Riichi | 1 han |
| Ippatsu | 1 han |
| Total | 2 han 40 fu · 2,600 points |
|---|
Non-dealer, East round, no dora, no honba.
Riichi · Ippatsu · Tsumo
| Riichi | 1 han |
| Ippatsu | 1 han |
| Menzen tsumo | 1 han |
| Pinfu | 1 han |
| Total | 4 han 20 fu · 1,300 / 2,600 points |
|---|
Non-dealer, East round, no dora, no honba.
Common combinations:
| Combination | Han |
|---|---|
| Riichi + ippatsu | 2 |
| Riichi + ippatsu + tsumo | 3 |
| Double riichi + ippatsu | 3 |
Ippatsu odds
We let four computers at normal level play 40,000 hands on this site's table and counted these timing-based yaku:
| Yaku | Share of wins |
|---|---|
| Ippatsu | 8.9% |
| Houtei raoyui | 0.77% |
| Haitei raoyue | 0.55% |
| Double riichi | 0.21% |
| Rinshan kaihou | 0.13% |
| Chankan | 0% |
Source: 40,000 computer hands on this site (all four at normal level), 33,226 wins. A win usually has several yaku, so the shares add up to more than 100%.
- Ippatsu was in 8.9% of all wins; among riichi wins, 20% had ippatsu.
- Ippatsu wins averaged 10,100 points, and 44% of them were by tsumo.
To try for one yourself, open a table of free online riichi mahjong — the computers play with you and count the points for you.
FAQ
How many han is Ippatsu?
Ippatsu is 1 han, and only after riichi (or double riichi).
Is ippatsu still on after someone calls pon?
No. Any chi, pon or kan by anyone between your riichi and your next discard cancels it.
Does my own closed kan after riichi cancel ippatsu?
Yes. Like Tenhou and Mahjong Soul, this site cancels ippatsu on a closed kan too.
Related yaku
Riichi 1 han（closed only）
Declare it with a closed tenpai hand for 1 han: requirements, the rules after riichi, ippatsu and ura dora, win rate and average result.
Double Riichi 2 han（closed only）
Riichi on your first discard for 2 han instead of 1: the rules, what stops it, examples and the odds of a tenpai start.
Try it at the table
Riichi Mahjong — Play Japanese Riichi Mahjong free in your browser against three AI opponents. Standard online rules with red fives, ippatsu and ura dora, a yaku guide, wait and furiten hints, and three AI levels. No sign-up.