Many blackjack players are aware that it is a good idea to double down on a hard total of 10 or 11. However, it can be more difficult deciding whether or not to double down on a soft hand, where one of the cards in the hand is an Ace. Luckily, the "Rule of 9" can help you to make the right decision every time you are dealt a soft hand and are trying to decide whether or not to double down.

Before we get into a discussion of the Rule of 9, it is important to note that you should only double down on a soft hand made up of an Ace and another card of 2 through 7. If your hand is made up of an Ace and an 8 or higher then you should not double down.

That said, whether or not you double down on a soft hand depends on what the dealer's upcard is. Basically, all you have to do is add the value of the dealer's upcard to the value of your non-Ace card. If this value is 9 or greater then you should double down. If the sum is less than 9 then simply hit.

There are a few exceptions to this rule:

• Never double down when the dealer is showing a deuce-the odds are not in your favor.
• When the dealer's upcard is 5 or 6 they are in a weak position and you should double down with all six soft hands, 2 through 6.
• Never double against a dealer's up card of 7 or greater.

So, let's say you've got an Ace and a 7 and the dealer is showing a 3. Added together this is 10, which means that you should double down. On the other hand, if you've got an Ace and a 2 and the dealer is showing a 4 then you should hit.