Eight Decks Can Be Used in Blackjack but Single Deck Is Best
Blackjack may be an easy game to play, but it is also the most skilful of all the games you will find on a casino floor. Contrary to the belief of newcomers, the objective is not to hit a score of 21 but to simply better the dealer’s score. What could be easier?
Knowing how many decks are in a blackjack table’s shoe is vital for serious blackjack players. © Getty Images
Knowing exactly when to draw cards against the dealer and when to stand firm is one of many angles that can increase the chances of winning. Likewise, splitting cards and doubling down at the right time is also strategically important.
There is a third angle that will help the chances of players keen to gain every last decimal percentage point of an advantage in their quest to beat the house. Yet few people ever stop to consider how many decks the house uses in blackjack games and how it impacts the chances of winning.
How Many Decks Are There in Standard Blackjack?
In a casino environment, blackjack is most commonly played with six or eight decks of cards. Rarely are just two decks used. Single-deck Blackjack is popular in downtown Las Vegas casinos, but in fear of players’ counting cards,’ they will offer odds of just 6/5 about a blackjack being dealt.
Some online single-deck blackjack sites still offer 6/4 about the perfect score. Meanwhile, double-deck blackjack, while scarce in land-based casinos, is relatively popular with some online casinos that offer live dealer-dealt games.
In blackjack, all decks are ‘full’, meaning they contain 52 cards: Four suits – which accounts for nothing in this game – four cards of each number, including four Aces valued at 1 or 11, and sixteen cards valued at 10 (the Kings, Queens, Jacks and 10s).
Why The Number of Decks Matters to Players
With automatic shuffling machines it can be difficult to identify how many decks a blackjack table is using. The best blackjack sites will display how many decks are in play in a particular game. The information is sometimes found towards the bottom of the screen. However, It can always be seen when clicking the ‘info’ icon.
The number of decks used in a game of blackjack matters because the probability of being dealt a blackjack – a two-card hand totalling 21, which consists of an Ace and a 10-value card – lessens as more decks are used.
Here is how the maths is made to quantify that statement for a hand of single-deck blackjack:
- There are 16 ten-value cards (10, J, Q, K) in a single deck and four Aces.
- To make a Blackjack, the first card you draw must be either an Ace or a 10-value card. 20 cards out of 52 are either 10-valued or are an Ace.
- If you draw an Ace first, the second card must be one of the remaining 16 ten-value cards (from the now 51 cards left). Or vice versa.
- The prospect of drawing an Ace first is four-from-52.
- The probability of drawing a 10-value card after drawing an Ace is 16-from-51.
- Alternatively, the likelihood of drawing a 10-value card first is 16-from-52.
- Then, the probability of receiving an Ace is four-from-51.
- So, the number of times you should have an Ace followed by a face card is 4 x 16 = 64.
- Mathematically, the number of times you will have a face card followed by an Ace is 16 x 4 = 64.
The calculations are complex, but the probability of being dealt a blackjack in a game that uses just one deck is 4.83%. This figure is achieved because there are 128 ways of being dealt a blackjack and 2,652 different hand combinations. 2,652 divided by 128 equals 20.72; as a percentage of 100, that number equates to 4.83%.
How the Likelihood of Blackjack Lessens With More Decks
The more decks used in a game of blackjack, the less likely a player will be dealt a blackjack. This is because each additional deck dilutes the concentration of Aces and 10-value cards relative to the total number of cards to the total number of cards.
Playing with two decks means there will be 104 cards in play. They will include Eight Aces and 32 cards with a 10-value. Resultantly, there are 512 different ways of being dealt a blackjack but 10,712 two-card combinations. 10,712 divided by 512 equals c20.92; as a percentage of 100, that number equates to c4.78.
This is how the probabilities of being dealt a blackjack change as more decks are added to the dealer’s shoe:
| Blackjack Variant | Probability |
|---|---|
| Single Deck | 4.83% |
| Two Decks | 4.78% |
| Six Decks | 4.74% |
| Eight Decks | 4.72% |
The facts are clear: Single Deck Blackjack is better than games using multiple decks when hoping to hit the hand that pays 6/4. However, there are additional advantages to playing the game when the dealer has just 52 cards to dispatch.
Single Deck Blackjack – The Advantages
In single-deck blackjack, the house edge varies depending on the game’s specific rules – such as the dealer being forced to hit or stand on soft 17 or doubling down after splitting cards is allowed. Here are some key rule variations that impact on the house edge:
- Dealer Stands on Soft 17: This reduces the house edge by about 0.2%.
- The Player can Double on Any Two Cards, which adds about 0.15% in the player’s favour.
- The Player Can Double After Splitting: This reduces the house edge by approximately 0.14%.
- Re-splitting Aces: This provides a small reduction in the house edge, around 0.05%.
- Early Surrender: If allowed, this can reduce the house edge significantly – by about 0.625%.
- Late Surrender: This is less beneficial than early surrender but reduces the house edge by about 0.07%.
Surrender poker is relatively rare in brick-and-mortar casinos, but the best live blackjack casino sites offer the variant, and it is something serious blackjack players should look for.
If you played with perfect basic strategy (making the statistically best play for every hand based on the dealer’s up card), the house edge in a single deck game is around 0.17% (under the most lenient rules) to 0.4%.
For true precision, it is recommended players consult a blackjack strategy chart tailored to the specific rules of the game they intend to play. Practising the game using a blackjack strategy calculator is also a good move.
But the ultimate advantage of ‘singe deck’ is the potential to card count. With just 52 cards in play, the best blackjack minds will know when there has been a shortage of 10-value cards and Aces. This means these cards are expected to arrive in a flurry – and high-value cards are massively advantageous to players.
