Kan strategy
Kan is a naturally risky action, due to the nature of kandora. When a player calls kan, any player - including the kan-declarer's opponents - may benefit from the kandora. Therefore, some assessment should be made when calling kan.
Assessing kan
Advantages
- Reveals an extra kandora. Players in riichi also benefit from kan uradora.
- Gives an extra tile draw, with a chance for rinshan if in tenpai.
- Increases the hand's fu.
Disadvantages
- Opponents can benefit from kandora if they win.
- The kanned tiles cannot be discarded or used in the hand.
- Reveals the called tiles in your hand.
- An open kan will open your hand.
Kan during riichi
When playing with real tiles, players in riichi must always be aware of whether a kan call can legally be called. Players using game software or online platforms do not need to be aware because the programs handle the situations for them.
Kan when likely to win
Kan is an aggressive move. You only benefit from kan if you win, and if you win, your opponents don't benefit from kan dora. Therefore, you should prefer to call kan when you believe you have a high chance of winning. For example, kan when you are already in tenpai (and no one else is in tenpai), and kan with a good 1-shanten hand if early in the game (turn <8).
Players in riichi benefit from twice the dora (kandora + kan uradora), so a kan during riichi is especially helpful.
Conversely, if an opponent is in tenpai, you should not kan, unless you are already in tenpai or very desperate. When you and an opponent are in tenpai, the decision to kan will depend mostly on point standing and your tenpai wait (prefer to kan with a good wait and prefer to kan when behind).
Situational analysis
Kandora increases the score of everyone's hand. Therefore, the decision to kan can change depending on the point standings and current round.
- Players far ahead in the lead should not kan. The extra points benefit your opponents more than you: extending your lead doesn't help you much, but your opponents can certainly use the points to surpass you.
- Players that are desperate for points - e.g., those behind near the end of the game - will prefer kanning.
Also, if far behind around all last and if winning is unlikely, you may want to kan to increase other players' hand values. If a player deals in, they'll have to pay more.
Fu
If the hand has 3 han or lower, the extra fu from kan can increase the hand score.
| English | Romaji | Simples | Honor/Terminal |
|---|---|---|---|
| Open kan Added kan |
Daiminkan Shouminkan |
8 fu | 16 fu |
| Closed kan | Ankan | 16 fu | 32 fu |
A closed kan with an honor/terminal tile gives 32 fu, which is not far off from gaining +1 han. As the most extreme example, a 3 han 40 fu ron would give 5200 points; declaring a closed kan with an honor/terminal upgrades it to 3 han 70 fu, a mangan (8000 points). Closed honor/terminal kans are thus very strong.
The other types of kan only give a small boost to score due to fu, so it should only be accounted for in tight point situations. For those types of kan, the main point boost will come from kan dora.
Don't open the hand to kan
If the hand is closed, almost never call open kan. The point boost from riichi is bigger than the points from kan (unless you get 4 kan dora).
If the hand is already open, it's ok to call open kan if the hand is likely to win.
Don't kan if the tiles can be used elsewhere
When the tiles used in a kan can be used as a pair, part of a sequence, or be useful as a floating tile, don't kan.
Example:
Draw:
The manzu can be treated as 
+ ; declaring kan breaks the 23-man sequence and thus results in a loss in speed.
If 1-man is drawn after, the shape becomes 
+ , so a kan is safe.
Example 2:
Draw:
The hand is in a sticky iishanten, with 3 groups + 1 pair complete, waiting to form a joint. Since the fourth 4-man can be used as a stronger floating tile than 1-pin, don't kan right now.
Defense
A player in betaori (full folding) should usually avoid declaring kan, because it removes four discard options from your hand, and may increase the opponent's score. For added kan, there is an added risk of chankan.
Any player can apply kabe when somebody calls kan. If all four tiles are visible, e.g. from an opponent's kan call, then it will make certain types of wait impossible. For example, If a kan of 3 is called, then the wait patterns of 23, 34, and 13 of the same suit are impossible. Thus, 1 and 4 become safer. If all four tiles are in your own hand, then there's no need to actually call kan in order to benefit from kabe.
If you have no safe tiles, a possible play is to call kan and hope to draw a safe tile. However, since this will likely increase the opponent's score, this is somewhat dubious. In addition, the kan tile could become safe later (e.g., becoming suji), and then you will lose four tiles. Therefore, avoid doing this unless it's late into the hand.
Shifting the draw
When a kan is called, one tile from the live wall shifts over to the dead wall. Therefore, kan can be used to deny ippatsu and/or the haitei draw.
Delaying kan
Kan is not mandatory, so players do not have to call kan immediately. Instead, they can keep the fourth tile in their hand, declaring kan if/when appropriate. This gives more flexibility - e.g., if you draw the 4th copy of a tile, then an opponent declares riichi on the next turn, you will be glad that you did not kan. However, delaying the kan will often reduce tile efficiency (if you are not using the tile for the hand).
Under most circumstances, you should not call kan if it would break up a sequence. For example, if you have a 555567 in your hand, it can be considered as two groups: 555 + 567. Calling kan would ruin the 567 sequence, thus slowing down your hand. But if you then draw the 8, then the sequence is retained, so kan no longer slows the hand.
Summary
The most important factors in calling kan are your % chance to win, the current point standings, and tile efficiency.
- Kan when likely to win (tenpai; early 1-shanten and no other player in tenpai).
- Prefer to kan when behind and not kan when ahead.
- Even when ahead by a lot, calling kan when in tenpai can be good for the extra draw/points.
- Even when behind, don't kan if winning is unlikely (unless last in all last).
- Don't kan if it would slow down the hand.
External links
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