It is something that is heard all the time when it comes to blackjack: the fewer the number of decks used in blackjack, the better your chances of winning. However, is this really true? Why is this said so often? After all, the overall proportion of every rank of card is the same irrespective of how many decks have been shuffled together.

Fewer Decks = More Blackjacks

The main reason why fewer decks are better for players is that, in one deck, exactly 1/13th of all cards are Aces. Therefore, yes, the initial proportions of card values with respect to one another is equal despite how many decks you play with. The reason why people are dealt more blackjacks with a smaller number of decks is that the effect of removing a card from the game is more with fewer overall cards.

Odds of Drawing Blackjack in a Single-Deck Game

To calculate the probability of drawing a blackjack from a single deck, all you need to do is multiply the odds of getting an Ace with the odds of drawing any card which has a value of ten points. A single deck of fifty-two cards has four Aces and sixteen cards that have a value of ten points, namely four Kings, four Queens, four Jacks and four Aces.

This means that the probability of getting an Ace from the deck is 4/52, which can be simplified to 1/13. Once an Ace is drawn, the likelihood of getting ten-point cards is 16/51. The first probability is based on a deck of fifty-two card cards, but since one card has already been drawn, the possibility of drawing one of sixteen ten-point cards is from a deck of fifty-one. This change in the divisor is the main reason why a smaller number of decks becomes advantageous to the blackjack player and puts the house at a distinct disadvantage.

So from the experiment given above, the probability of drawing a blackjack from a single deck is 4.83%.

Now when one more deck is added, this percentage drops to 4.78%. The casino has reduced your likelihood of getting a blackjack by 0.05%. Even though this may seem small, it is important to remember that each one of the lost blackjacks you lose was a win under standard casino rules at a 3:2 payout. Losing those payouts can make a big impact on your bottom line, as well as on the casino’s.

Double Downs Work Better with Fewer Decks

The same phenomenon that makes blackjacks more probable with fewer decks also affects the likelihood of a successful Double Down. If you double your initial hand, say 6 and 5, there is a greater chance of drawing a face card and bring the total as close to 21 as possible without exceeding.

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