Gambling Tips >Blackjack


By Henry Tamburin

If you have a choice of playing blackjack in a casino where the dealer deals the cards with a single or two decks as opposed to  6 or 8 decks which one would you play? In most cases, a single or two-deck game has a lower casino edge for a basic strategy player than a game dealt with 6 or 8 decks of cards. Often the difference is about 0.5%, which doesn’t seem like much but in the long run it means more money in your pocket rather than the casino coiffeurs.


When you first think about it, it's hard for players to understand why the casino's edge increases when more decks of cards are put into play. There are in fact several reasons for this and for the sake of argument let’s compare a blackjack game dealt with one deck of cards vs. six- or eight-decks of cards.

There are more blackjacks in single deck games vs. multiple deck games.

You're probably wondering how this can be since the percentage of aces and tens in a single-deck game is the same as in 2, 4, 6, or 8-deck game.  That's true but the effect of removing a card from a single deck of cards affects the percentages of the remaining cards to a much greater extent compared to multiple decks of cards.


The following chart summarizes the probabilities of getting a blackjack with a different number of decks.  Note that a player will, on average, get fewer blackjacks as the number of decks increases. In fact, you'll only be 98% as successful drawing a blackjack in an 8-deck game compared to a single-deck game, which makes the single-deck game better.




# Decks                      Probability    
1                                  1 in every 20.72 hands
2                                  1 in every 20.93 hands
4                                  1 in every 21.02 hands
6                                  1 in every 21.07 hands
8                                  1 in every 21.07 hands


Although getting more blackjacks is good for the player, it's even better when you get a blackjack and the dealer doesn't. Which brings me to the second point.

The dealer's chances of duplicating our blackjack decreases as the number of decks decreases”.

When you get a blackjack and the dealer doesn't, you get paid at 3 to 2. But if the dealer also has a blackjack, it is a tie and you win nothing. Therefore, the less chance the dealer has of getting a blackjack, the more times you will be paid the bonus 3 to 2 payoff and your earnings potential will increase.

The chart below shows that there will be more blackjack pushes in multiple deck games compared to single deck games because the dealer will be getting more blackjacks as the number of decks increases. Therefore, in single deck games you will be paid 3 to 2 more often and therefore win more.




Number of Decks     Probability
1                                  1 in every 27.22 hands
2                                  1 in every 23.74 hands
4                                  1 in every 22.34 hands
6                                  1 in every 21.92 hands
8                                  1 in every 21.71 hands


The third reason why the casino's edge increases when more decks are put into play is:


"When you double down, you are more likely to get the card you want in a single deck game compared to a multiple deck game".


The mathematical basis for this is simply that the effects of card removal are much more pronounced in single-deck games vs. multiple-deck games.

Take the case of a player drawing a 6 and a 5 against a dealer's 5 upcard. The player is looking for a ten-value card to give him a 21. In a single-deck game the chance of the player getting a ten-value card after the players 6 and 5 and dealer's 5 are removed from the deck is the ratio 16 over 49 or 32.6% chance of getting a ten. In a six-deck game, the probability becomes 96 over 309 or 31.07% chance of getting a ten. A player is 5% less likely to reach 21 in a 6-deck game compared to a single-deck game. Or to put it another way, you are more likely to be successful doubling down in a single-deck game compared to a multiple-deck game making a single-deck game the better game.


Given a choice, a single- or double-deck game is a better choice for the basic strategy player as long as the casino hasn’t introduced several unfavorable rules in the process. If you don’t know which blackjack rules are unfavorable, I strongly suggest you read a book on blackjack and bone up on this important point before you play.

Note: The Ultimate Basic Strategy Cards are available in my online store at I highly recommend them.