Mahjong Fundamentals 7: When to Defend

Deciding when to push in riichi mahjong is a very delicate balance to try and find. A player who rarely defends will usually not have a very good win-rate, at least against experienced players, but at the same time a player who always folds at the first sign of danger will typically struggle as well. Push/fold judgement is incredibly tricky and typically very situational, and is something that even very high level players will commonly disagree on in specific scenarios.

That said, a key thing to learn as a new player is when you should fold, and there are still many situations where the push/fold judgement is relatively clear-cut and there is an agreed ‘correct’ answer amongst most high-level players.

When to consider folding

For the most part you can completely ignore defence against your opponents except for two situations:

  1. A player has declared riichi
  2. A player has an open hand that is confirmed mangan or better, especially if they have called more than once

This is because it is incredibly difficult to read whether a fully closed hand is tenpai without having declared riichi, and because dealing into inexpensive open hands is usually not a huge problem. If you’re playing in a game where nobody has declared riichi or made any calls, then it’s safe to focus on your own hand and not worry too much about what your opponents are doing. Obviously sometimes players will be in tenpai and won’t have declared riichi, or will have yakuhai and a hidden dora 3, but it is not a good strategy to break up otherwise good hands on guessing that these might be the case.

One exception is for players who are almost certainly pursuing a flush hand (i.e. honitsu or chinitsu) and have begun discarding tiles from the suit they appear to be collecting. This usually indicates that they are tenpai and it’s worthwhile trying to play around their hand.

Situations to fold

So, you’re halfway through a hand and the player opposite you declares riichi. Do you fold, or do you push and try and win? The answer depends on your hand.

In general, you should fold if:

  • You are tenpai but your score is below 7700 and your wait is bad
  • You are 1-shanten and your expected hand value would be below 7700 or you don’t have a guaranteed good wait
  • You are 2-shanten or higher

In these situations we should fold if advancing our hand would require us to discard a tile that is not safe. Obviously if we can continue to push our hand whilst discarding 100% safe tiles (genbutsu) then it is OK to do so.

As was discussed in the last article, mahjong is a game where you won’t be the winning player the majority of the time. It’s important to recognise this when faced with situations where folding is the right choice, and not to be too aggressive and try to win hands when the odds are stacked against you and you have good defensive options.

Situations to push

So what about when someone declares riichi and we have a good hand? If the hand is good enough, then it’s worth pushing.

In general, you should push if:

  • You are in tenpai and your minimum value is above 3900 points with a good wait
  • You are in tenpai and your minimum value is above 7700 points with a bad wait
  • You are 1-shanten and your worst hand development guarantees you 7700 points and a good wait

Typically any wait that is five or more possible tiles is considered a good wait, and any wait on four or fewer tiles is a bad wait. When chasing against someone else in tenpai, the wait is very important as once you push the game effectively becomes a tile-flipping contest for whose winning tile appears first. In these cases a ryanmen wait gives you double the chance of winning (8 tiles) over a penchan or kanchan wait (4 tiles).

It should be noted that these situations are quite rare. Typically if you are already in tenpai you will have declared riichi, and therefore cannot decide to fold anyway, and hands that are 1-shanten or higher with both good wait and mangan guaranteed are not that common.

The Grey Area

The principles lined out above are general rules of thumb for steering your decision in push-fold on the assumption that all 100% safe tiles you could discard would involve breaking up your hand, and any tile you need to discard to progress the hand is likely to deal in. Often in mahjong this is not the case, and we can advance our hand by playing tiles which are not 100% safe but are partially safe (through techniques like suji or kabe as discussed in the previous article). This, however, is something of a dark art, and is much too complex to lay out in a single article, let alone one aimed at covering fundamentals!

In general, bear in mind the three fundamental aspects of your hand, which in order of importance are: your shanten, your value, and the quality of your waits. If all three are bad, then definitely fold (and fold by discarding the safest tiles you can). Likewise if all three are good, then push pretty much any tile you need to. If you have one or two out of three, then it really depends on how risky the tile you need to push is. But don’t be afraid to fold good hands, and in particular don’t focus so much on what your hand could be that you ignore what it currently is. If you have a potential haneman at 3-shanten you should still play defensively a lot of the time, because the chance you’ll reach tenpai without dealing in is very low.

It’s also worth being aware of the points situation, particularly in later rounds. If you are far behind in South round you should typically be more inclined to push, particularly if your hand has high value. Vice-versa, if you are leading in the later rounds of the game you should be more inclined to fold if someone reaches tenpai before you.

Examples

Here are five example hands, for each one consider whether you want to push or fold this hand, and which tile would be best to discard:

1)

There is a dealer riichi to our left. Our hand has two dora and so good value potential, however we are still far from tenpai and so it would be wise to fold here. We should discard or , as they are the only 100% safe tile in our hand.

2)

In this case there is a riichi to our left. Our hand is 2-shanten, with low chance of becoming mangan and a couple of awkward shapes to be completed. We should fold here by discarding , as it is our only safe tile.

3)

Here we have a late dealer riichi to our right. We have just reached tenpai, and through discarding we can be tenpai for a hand that is at worst a pinfu dora 3 mangan, and potentially a haneman if we win on . It is worth noting that we do not have a particularly good wait, as three of the tiles and one tile have already be discarded. However the value here is enough that it is OK to push .

It also helps that is covered by suji from a wait, and is double one-chance from a wait (you can see three and three ), and therefore despite being a middle discard, is relatively safe to push out.

As a side note, you should not riichi here on the as your hand already has sufficient value without it.


Push/fold decision-making is a difficult aspect of riichi mahjong to master, and this article provides only a basic introduction to the topic. There are a lot of factors at play when choosing whether to defend or push, and two situations are rarely the same. For more detailed discussion on defence, please read Chapter 8 of Riichi Book 1, as well as this article series by Puyo. Also bear in mind that hindsight bias can be very strong with push/fold – just because a tile would have passed does not mean folding was necessarily the wrong choice with the information you had at the time.

In the next article, we’ll switch back to looking at tile efficiency in a bit more depth, and will look at some of the more common complex shapes that you’ll encounter in mahjong, along with how to identify when neighbouring tiles help or hinder each other.

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