Why Does Deck Size Matter in Blackjack?

The more decks that are utilized in a blackjack game, the higher your odds, as you have probably heard several times.

Have you ever thought about why this is?

After answering a question from a friend of mine who doesn’t gamble much, I was motivated to write this blog article. He started learning blackjack as he got ready to go to a bachelor party in Vegas. Everyone seemed to agree that having fewer decks is preferable, but he wasn’t sure why. After all, he argued, no matter how many decks are mixed together, the total proportion of each card rank remains the same.

Fewer decks mean more blackjacks

The main justification for our claim that using fewer decks is preferable for players is the fact that exactly one-third of the cards in each deck are Aces.

Yes, my friend was correct; regardless of how many decks you use, the starting ratios of card values to one another are equal. The impact of eliminating a card from the game is larger in a game with fewer total cards, therefore you’ll be dealt more blackjacks with a smaller shoe.

Odds od drawing blackjack in a single deck game

Let’s begin by estimating how frequently a player will draw blackjack in a game with only one deck. You only need to calculate the odds of drawing an Ace by the odds of drawing any card worth ten points to determine the likelihood of obtaining a blackjack from a single-deck shoe. Four Aces and sixteen cards of ten points, including four tens, four jacks, four queens, and four kings, are known to be present in a single deck of fifty-two cards.

Accordingly, the odds of drawing any Ace are 4/52, which we may reduce to 1/13. The likelihood of drawing any ten-point card after drawing your Ace is 16/51.

A reduced number of decks is advantageous to the blackjack player and disadvantageous to the house because of this shift in the divisor.

Since you might theoretically receive a blackjack with either a ten-point card OR an Ace at the start, you actually need to double your result to get an accurate estimate of the likelihood of drawing a blackjack from a single-deck shoe.

In total, 4.83% of draws from a single deck shoe will be blackjacks. It is calculated by multiplying the odds of drawing an Ace (1/13) by the odds of drawing any card worth ten points (16/51), then by two.

Odds od drawing blackjack in a two-deck game

Let’s look at the chances of drawing a blackjack when you start with 104 cards rather than 52 to give you an understanding of the statistical difference between one and two decks.

In a two-deck shoe, the odds of drawing any Ace are 8/104. Following that, there is a 32/103 chance of drawing any ten-point card from the same shoe. The outcome of adding those two together and doubling the answer is 4.78%.

In a one-deck shoe, the probability of drawing a blackjack is 4.83%. In a two-deck shoe, the probability of drawing a blackjack is 4.78%. The casino has cut your chances of drawing a blackjack by 0.05% by adding a deck without altering the game’s rules. However, keep in mind that each of those lost blackjacks would have resulted in a win with a 3:2 payout under normal casino regulations. Losing those 3:2 rewards has a significant negative effect on both your and the casino’s bottom line.

The reason double-downs work better with fewer decks

If you’ve been paying attention, you’ve probably already realized that the same factor that increases the frequency of blackjacks with fewer decks also influences the chances of a successful Double Down. If the game uses fewer decks and you double your starting hand (6 and 5), you’ll have a better chance of drawing a face card to make a total of 21.

Here’s where it gets tough; keep in mind that with lower deck counts, your dealer also gains from these modifications. The player doesn’t have a guarantee of getting more blackjacks. This reality doesn’t affect the game as much as it might because in blackjack, players win 3:2, while the house only makes even money. Additionally, while the player can Double Down, the dealer cannot. The player now has a greater advantage over the dealer thanks to the additional twofold win.

Conclusion

When all other factors are held constant, which means that the rules are essentially the same, a blackjack game that builds the shoe with fewer decks is better for the player. Casinos that provide single-deck blackjack with a 6:5 or even 1:1 payout for player blackjack are one scenario I’d advise blackjack players to avoid. The inference is that the casino will only provide you these better single-deck odds in exchange for a lighter player blackjack penalty. Don’t play games that don’t pay out at the standard 3:2 ratio simply because the single deck configuration appeals to you.

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