Beyond Basic Strategy: Maximizing your Double Downs By Fred Renzey 17 July 1999
Have you ever noticed that a basic strategy chart for single- or double-deck blackjack is more aggressive than for six-deck shoe games, particularly where doubling down is concerned? Why is that? First of all, understand that whenever you double down, you don't have a 10 in your hand. That's key. Now notice that when you pull three non-10s (your hand and the dealer's upcard) from a 52-card pack, the remaining 49 cards contain 32 1/2% 10s (16 out of 49). But if you took those same three non-10s from a six-deck shoe, the remaining cards would contain only 31% 10s (96 out of 309). Therefore, you have a little better chance of catching a 10 to your double down with fewer decks.
For this reason, some single- or two-deck double downs that were just minimally profitable now become unprofitable when playing with six decks. As an example, six-deck basic strategy says you shouldn't double down with a hand like 9 against a deuce (while you should when playing with one or two decks). And indeed with six decks, you shouldn't--USUALLY!
"Usually" is the key word here. The basic strategy gives you your best play assuming that all cards except for the three that make up your hand and the dealer's up-card are equally available. In reality, however, their availability varies as cards are dealt out. And if you've got your eyes open, even without being a card counter, you'll often be in a position to notice that all the remaining cards are not equally available. When would that be? Consider the following scenario...
You're playing with three other players in a six-deck face-up game. You are at third base. The dealer has a deuce up. The other players have finished playing their hands and the board looks like this:
DEALER 2 up
YOU 6/3 CENTER FIELD 8/2-5 2ND BASE 7/4-4 1ST BASE 10/6
The first baseman stood pat with 16. The next player doubled down with 11 and caught a 4. The man to your right then doubled with 10 and blanked with a 5. Now it's your turn. What should you do with your 9 against the dealer's deuce? Before answering, notice that the board contains quite a few low cards and only one 10.
Without knowing anything else about the cards that have been dealt thus far in the shoe, you can see that your chance to snag a 10 is now similar to what it would normally be with fewer decks. Your correct play in this spot is to double down. That's right; double with 9 against a deuce even though multi-deck basic strategy says to hit. This is reacting to information that the basic strategy doesn't take into account. It's going beyond the basic strategy. It's more efficient and more productive than the basic strategy. Now, how do you know exactly when you should pull the trigger and double rather than hit?
BOARD COUNTING The technique a non-card counter can use to uncover these situations is called "board counting". With hands this marginal, you don't need to count down the whole shoe from the get-go to find out that it's probably better to go a different way with your hand. You simply take the information that's available right now. What you do is measure the proportion of high to low cards that have appeared during this hand by counting all the 3s, 4s, 5s and 6s as one point apiece. Then count up all the 10s, jacks, queens and kings as minus one point each. Ignore the other cards. After scanning the entire board in this manner (including your own hand and the dealer's upcard), subtract the minus cards from the plus cards.
Now let's go back to the hand illustration above. Looking at all the cards, what is your net "board count"? It's +5 (one 10 subtracted from six 3s through 6s). Remember that number. Why? Because when your board count is +5 or greater, you should double down with the following two hands in six-deck play:
9 against a deuce ace/8 against a 6 (If it's less than +5, just follow the multi-deck basic strategy).
With a board count of +6 or greater, it also becomes correct to double down when you have:
11 against an ace
At these times, your chance to catch a 10 will have improved enough to make doubling the better play. A few of your "stiff" hands in multi-deck blackjack can also be played more efficiently with the use of the board count, but that's a lesson for another day.