After a good weekend off, I am now continuing the ongoing series on doubling down strategy for blackjack. I have already covered the basic strategy for doubling hands of nine, 10 and 11. In this post I will discuss the strategy for a soft 13. It should be noted that you will never double a hard 12-21, which is why those hands aren’t being covered in this series.
If you have a soft thirteen (ace, two), whether or not you should double depends on the dealer’s up card. If the dealer shows a five or six, you should double. If the dealer shows anything else, you should take a hit. You should never stand on a soft 13.
As always, blackjack basic strategy takes into account that there are more cards with a value of 10 (4/13) than any other value (1/13 each). For that reason, basic strategy plays off the probability of a the dealer having a 10 in the hole and you or the dealer drawing a 10. Therefore, if the dealer shows a five or six, he has a good chance of having a 15 or 16, which are not only stiff hands (12-16), but the two worst hands in blackjack. Why are they so bad?
The dealer doesn’t have the option of standing on a stiff hand, so he has to hit. If he does, his chances of busting are very good. If the dealer has a hand of 15, only five cards (2, 3, 4, 5, 6) will improve his hand, while seven cards (7, 8, 9, 10, J, Q, K) will cause him to bust. If the dealer draws an ace, that gives him a hand of 16, which is another stiff hand. If the dealer has a hand of 16, only five cards (ace, 2, 3, 4, 5) will improve his hand, while eight cards (6, 7, 8, 9, 10, J, Q, K) will cause him to bust. That means with both hands, when the dealer hits he has 8/13 odds against him. Since you have a soft hand, you don’t have to worry about busting. For that reason, it is best to double your bet so you make more money on the high likelihood of winning.
Even though hands of 12, 13 and 14 are also stiff hands, you don’t want to double down if the dealer shows a two, three or four. That is because, though the dealer still has a good chance of busting, the odds of him doing so are not as high. Also, one of the advantages of a soft hand is that you can be more aggressive when hitting in an attempt to improve your hand, since there is no possibility of busting. However, if you double down then you can only receive one more card. If you receive a card that doesn’t help your hand, you can only hope the dealer busts and you basically lose the advantage of your 13 being a soft hand rather than a hard 13.
Or look at it this way: If the dealer busts it doesn’t matter what hand you have. If he doesn’t, however, you need to use that soft hand to your advantage to draw a good hand. If you have a soft 13, that means five cards (4, 5, 6, 7, 8 ) can help you and 8 cards (ace, 2, 3, 9, 10, J, Q, K) give you a stiff hand. What that means is that if you have a soft 13, 8/13 of the cards you could draw would make you want to draw another card if you were to follow basic strategy. If you double down, though, you are unable to do so.
Therefore, you should only double down on the two hands (15, 16) where the dealer has the highest probability of busting. That is why the proper strategy for a soft 13 is to double down if the dealer shows a five or six and hit on any other hand.