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Blackjack Decks Explained: Complete Guide

Blackjack is one of the most popular card games played at casinos, whether that be in online or brick-and-mortar environments. As a player, the main objective of blackjack is to secure a stronger hand (set of cards) than the dealer. Although multiple players will usually be seated at a blackjack table at any given time, each is locked in an individual battle with the dealer – not with one another.

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The strongest hands are those which carry a card value closest to 21, with blackjack – which amounts exactly to 21 – the best set of cards to have.

There are different versions of blackjack available; the format used will usually depend on the geographical location of the casino (or, in the case of online casinos, the traditional/most-popular version amongst its target audience).

Furthermore, there are also differences in the volume of decks casinos use to facilitate a game of blackjack. Although most casinos will deploy either six or eight decks, there are some that operate online blackjack tables with as little as a single deck in circulation; the fewer decks there are, the greater the likelihood of a player victory.

A more detailed reason for this will be provided at a later stage, but, in general terms, the catalyst for this change in probability can be said to be driven by a reduction in house edge – the advantage the casino leverages over players in order to tip the balance in their favour and ensure their business remains a profitable enterprise.

This article reviews the different numbers of decks used in blackjack and highlights the impact this has on the game. Moreover, we will also discuss how using basic blackjack strategy can significantly increase your chances of winning at the casino and how this approach needs to be adjusted when applied to games carrying differing numbers of decks.

Before launching into our analysis, it is important to quickly note that online casinos almost exclusively use six or eight decks in order to conduct a game of blackjack. Therefore, in the sections below, comments regarding single-deck and double-deck games are only relevant in the context of land-based casinos.

Single-Deck Blackjack

Clearly, a single-deck game, which uses just one deck of cards, is a contest that facilitates the fewest number of cards out of any blackjack variant.

A standard playing deck holds 52 cards, possessing 36 numbered cards, 12 face cards, and 4 aces. In blackjack, cards 2-10 (numbered cards) carry the same value as their respective numbers, whilst face cards (King/Queen/Jack in all four suits) are worth 10, and aces are valued at 1 or 11.

As the target number for all participants is 21, cards representing the values of 10 and 11 (ace) provide a suitable pathway towards a strong score. Therefore, 10s, face cards, and aces are the most favourable to receive when being dealt your opening hand (otherwise referred to as hole cards).

However, if issued at a later stage, these cards have a higher likelihood of increasing your score to over 21, rendering your hand bust, and resulting in you exiting the round.

A blackjack is the game’s perfect score (otherwise referred to as a natural), whereby the player receives a 10/face card, plus an ace, as their two hole cards. As this score is unbeatable, the opposing participant (player or dealer) must also have a blackjack in order to tie the game – otherwise, the winner will be automatically confirmed.

As alluded to in the previous section, the fewer the number of cards being used, the more advantageous the playing conditions. In essence, this boils down to the probability of certain cards – specifically the aforementioned 10-value cards and aces – being allocated to the player. This point can be illustrated through an analysis of two real-world blackjack situations:

Example 1

In a single-deck game, a player is dealt an ace as their opening hole card. In this scenario, 16 of the remaining 51 cards in the deck hold a value of 10 (four ten cards, 12 face cards – King/Queen/Jack in each of the four suits). This means that 31.37% of the outstanding cards carry a value that could result in the player hitting a natural.

If the player received an ace as their first card in a six-deck game, the percentage of available 10-value cards would decrease, therefore reducing the chance of victory. Indeed, after removing one ace from six decks, there are 96 remaining 10/face cards in the game, which equates to 30.87% of the total card sample.

Example 2

In a single-deck game, a player’s first hole card carries a value of 10. Therefore, the original four aces are present in the remaining set of 51 cards. Therefore, 7.84% of cards still available in the deck are aces, which could be paired with the player’s opening hole card to produce a natural.

However, if the same circumstances apply to a six-deck game, the probability of securing a perfect score is reduced. This is because only 7.72% of the outstanding cards are aces, making it less likely that one of these cards will be drawn to complete the player’s set of hole cards.

In a nutshell, the fewer the number of decks in circulation, the more likely a player will land a blackjack, resulting in a higher win probability. The house edge in single-deck blackjack games is 0.16% - a full half of a percentage point less than in eight-deck blackjack. This may not seem like a huge difference, but in a game of slim margins, it is a significant decrease – besides, any advantage conceded by the casino should be celebrated as a bonus!

Double-Deck Blackjack

As its title suggests, double-deck blackjack is conducted with two card decks, which amounts to 104 cards overall. In a double-deck game, there are 32 cards in-play which hold a value of 10, and 8 aces available. In the context of the examples above, if you draw an ace as your first hole card, the probability of receiving a face/10 card next is 31.06%. Conversely, if your opening card carries a value of 10, there is a 7.76% chance your second card will be an ace.

The house edge in double-deck Blackjack is 0.46%

Six-Deck Blackjack

The total number of cards in six-deck blackjack is 312 (6 x 52 cards). The amount of 10/face cards and aces included in a six-deck game are referenced in the examples provided in the single-deck section of this article.

The house edge in six-deck blackjack is 0.64%

Eight-Deck Blackjack

The multi-deck variant with the largest number of cards in circulation is eight-deck blackjack. Indeed, with 416 cards in operation, the number of possible hole card variations is at its highest in this game. With respect to the previous examples, the likelihood of receiving a face/10 card after drawing an ace is 30.84%. Alternately, you have a 7.71% chance of picking up an ace when your initial hole card holds a value of 10.

The house edge in eight-deck blackjack is 0.66%. Therefore, eight-deck blackjack facilitates the lowest probability of player success.

What is basic blackjack strategy, and how is its application impacted by the number of decks in a game?

When used correctly, basic blackjack strategy increases a player’s chances of winning. Working on a mathematical basis of probability, this methodology charts the optimum move a player should make when dealt specific cards. As this strategy highlights the ideal next move in every possible scenario, players wishing to deploy this approach have a significant amount of information to learn. Basic blackjack strategy is typically presented in a detailed visual matrix, which helps players efficiently identify their next move.

There are four moves a player may exercise after receiving their hole cards; however, whether they can undertake these actions is dependent on the card they hold and the respective casino rules in place.

After receiving their hole cards, players must pursue one of the following options:

Late Surrender – This option is not provided in all casinos and those establishments who do give players the opportunity to Late Surrender only permit this move before a ‘hit’ occurs (more on this to follow). The Late Surrender is typically used when the player’s hand is weak (i.e. totals 16). However, you must wait until the dealer has discovered whether they have landed a natural – if the dealer does deliver a blackjack, the player is unable to Late Surrender.

If you do opt to Late Surrender, you will automatically lose the round, but recover half of your betting stake.

There are some casinos which allow you to Early Surrender, which enables you to dispense your cards before the dealer turns over the face-down card. Theoretically, this means you could escape having to face the dealer whilst they hold a blackjack. Therefore, Early Surrender provides a greater advantage than Late Surrender. However, there are very few casinos that facilitate this option.

Split – Players are only able to split when the first card is a pair (i.e., each card holds the exact same value). Although this rule includes all cards which hold a value of 10 (i.eJack and a Queen), players are generally advised to never split this type of pair. That being said, there are one or two contexts in which this action would be encouraged. Splitting cards basically creates two separate games in one, with each of your hands active and compared independently to the dealer’s single card set. It also worth noting that hands require additional matched wager.

Double-down – At certain times, the optimum move will be to double-down, whereby the player doubles the stake they originally placed at the beginning of the game. This action is reserved for when players are in possession of an extremely strong hand or appear to have a superior set of cards to those held by the dealer. By betting more aggressively in this moment, players can capitalise on positive situations and therefore potentially increase the amount of money they win.

Hit/Stand – In your bid to get as close to 21 as possible, you must decide in each round whether to hit (request an additional card) or stand (retain the same cards). This decision should be based on the strength of your own hand and how this compares to the dealer’s set of cards.

Although basic blackjack strategy generally remains consistent regardless of how many decks are in play, there are certain occasions where this methodology is tweaked. This is because the volume of decks impacts how often cards will potentially appear in a single blackjack game – the more cards that are used, the fewer times the same card will repeatedly surface. As a consequence, the probability of specific outcomes change.

As there is a difference in the likelihood of certain card combinations materialising when playing with different numbers of decks, the ideal move in each scenario – which is exclusively based on the probability of a favourable card being dealt – is therefore also re-calibrated.

Basic blackjack strategy charts are available for single and all multi-deck games, so you will always be able to access the information you require to successfully navigate the specific game you are playing.

Blackjack Decks FAQ

How many decks is best for blackjack?

In general, single deck games are better for players since they tend to have a lower house edge compared to multiple decks online blackjack games.

How does the number of decks affect card counting?

Since card counting techniques rely on tracking the specific cards in the deck, increasing the number of decks makes it much more difficult.

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