Doubling down is one of the most thrilling moves in Blackjack. It allows you to double your bet in the middle of a hand in exchange for one extra card. It’s a risky gamble, as it usually ends your betting - if you receive a particularly low second card you can’t hit again.
This can lead to more timid players avoiding the double bet, and more adventurous players making it far too often. It's important to try and strike a balance between sensible safe play and risky double downs in order to maximise your potential winnings.
Fortunately, basic strategies for Blackjack have been meticulously mapped using mathematical probability, designed to tell you exactly when is best (in the long run) to double down. There are three situations when it’s best to double down, explained below. In all of these situations you can’t go bust and are in the most likely position to finish with a high hand, while the dealer is in the statistically most likely position to lose the hand.
When you are dealt a total of 9, double down when the dealer shows a card between 2 and 6 (any card below 7, not including the Ace). This must be a hard 9; meaning there is no Ace in your hand – so the combinations could be 2-7, 3-6 or 4-5. If you have A-8 (a soft 9), it’s best to stand, regardless of what the dealer shows.
If you have an Ace and either a 5, 6 or 7 giving you a ‘soft’ total of 16 to 18 and the dealer shows a card from 2 to 6, this is a great time to double your bet. With an Ace and a lower card (2 to 4) it is better to just hit, as you are less likely to end with a high hand.
A hard 10 or 11 puts you in a powerful position – that is, with any two cards, not including an ace, that make 10 or 11 (2-8, 2-9, 3-7, 3-8, 4-6, 4-7, 5-6). If the dealer has a lower total, double down.
In almost every Blackjack game this strategy should stay true. However, be aware that the rules of Blackjack do vary between casinos, which can affect your decision making. If it’s possible to double with 3 or more cards, then you may find additional hands when you could double down, so pay attention to your total. On the other hand, you might find situations where the rules say you can’t double when the strategy says you should – such as on soft hands (those with an Ace). If you can’t double down when you'd like, be sure to hit instead.