Do Single-Deck Blackjack and Multi-Deck Blackjack offer the same odds

Many blackjack players believe that taking into account all factors, the odds of winning at a single-deck game are the same as experienced on a multi-deck shoe game. They believe that although an increased number of card decks are used, the identical number of cards is still involved; therefore even for an experienced blackjack player, or even a card-counter there is no advantage to playing in a single-deck game over a multi-deck game. This is not the case.

Putting nonmathematical considerations to the side e.g. single-deck games are easier to count successfully, Edward Thorp proved that a player's advantage diminishes as the number of decks utilised in the game increases. Adhering to blackjack basic strategy, the blackjack player has a 0.13% advantage over the casino in a single-deck blackjack game, but if a theoretical 5,000 decks were utilised then the player would be at a disadvantage of about 0.58% without tracking the cards. This makes logical sense due to the fact that the fewer cards used in a game, the m ore directly the removal of any number of them affects the distribution of the remaining cards.

Another reason to opt for a single-deck game as opposed to a six-deck game, whenever the rules are similar, is that you are less likely to get blackjacks in games that employ more cards. It sounds implausible, but compare the following two examples:

1. In the single-deck blackjack game there are 190 (20 x 19 / 2) possible two-card combinations involving the four Aces and sixteen ten value cards, 64 (4 x 16) of which produce blackjack, 64 chances out of 190 equals about 34%.
2. In a six-deck game, although the ratio of ten value cards to Aces remains exactly the same at 4 to 1, there are 7,140 (120 x 119 / 2) possible two-card combinations involving the twenty-four Aces and ninety-six ten value cards, a total of 2,304 (96 x 24) producing blackjack; 2,304 chances out of 7,140 equals just over 32%.

No wonder most casinos, if not all online casinos are moving towards offering blackjack games with an increased number of decks. Out of every hundred hands composed of Aces and ten value cards that are dealt from a shoe, the expectation of blackjack appearing in a six-deck game is nearly two fewer than it is from a similar single-deck game.

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