How many decks of cards are used in blackjack?

We’ll take a look at how the number of decks used in a game of blackjack impacts the house edge and card counting, and the number of decks used by Australian land based casinos.

Technically there’s no limit to how many decks of cards can be used in a game of blackjack. While a couple of mates playing at home can play a decent game of 21 using as little as one or two decks, casino blackjack is most commonly played with six to eight decks of standard 52 playing cards, excluding jokers.

How the number of decks affect the house edge

How many decks of cards in blackjack

The higher the deck, the higher the house edge.

When optimal blackjack strategy is employed, the theoretical house edge for a game of 21 is less than 1% depending on the rules in play, making this the most player friendly of all casino card games. However, the house edge can vary significantly depending on the number of decks of cards that are used per game and the rules that are in place, with a 0.5% house edge typically reserved for fewer deck games with player-friendly rules.

As more decks of cards are added, the house edge becomes higher and higher, growing even further with the introduction of new rules that have been implemented by land based casinos to give the house an extra advantage (for example, excluding doubling on soft hands, offering lower payouts for natural blackjacks, unfair Soft 17 rules, etc).


The reason for the variation in house edge is that the more decks of cards that are used, the lower your chances are of drawing a natural blackjack (a hand with a 10 value card plus an ace), with fewer decks giving you a better chance. With fewer decks in use, the dealer also has a lower chance of drawing a natural blackjack against the player’s natural blackjack, which means there is a lower chance that a pushed tie bet will occur.

Impact on card counting

Card counting is big in blackjack, with many players benefitting in big ways from being able to mentally calculate which cards have already been dealt versus which cards remain in the shoe in order to determine their next move.

With single deck blackjack, card counting could be mastered with some work even if you weren’t the most mathematically advanced type, with many card sharks publishing bestselling books teaching their card counting methods. However, the addition of each and every deck of cards makes card counting that little bit more difficult, so unless you’re a whiz with numbers or a maths genius, card counting with multiple decks is completely impossible for the majority of players.

Why some land based casinos use fewer decks

It wasn’t too long ago that casinos around Australia used the single deck blackjack format, with similar rules to those we’re used to seeing employed with online six deck blackjack games, which is what put the house edge around the 1% mark. As more players honed their blackjack strategy and card counting began to grow in popularity and effectiveness, the casinos had to put certain provisions in place to protect the house against these player-friendly rules.

Initially, casinos kept the single deck format but introduced some rules that were so unfavourable to players that recreational punters were turned off the game entirely, which is what led to the introduction of the higher deck games, which you’ll find at some casinos. At Australian casinos like Crown Melbourne, Crown Perth and Star Sydney, blackjack games commonly use between four and eight decks.

However, to keep players happy by continuing to offer blackjack games using fewer decks of cards, some casino vendors imposed less player-friendly rules, like restricting splits, imposing lower betting limits and paying less for blackjack wins. So while players can benefit from using fewer decks, the unfair rules make the game work in the houses favour.

These blackjack games using fewer decks and limiting rules have become favoured by Australian casino vendors as they are highly favourable to the house, much to the disdain of punters. Dedicated blackjack players should consider switching to play online where the probabilities and house edges are more favourable to the player.

Benefit of online play

Online gambling was made illegal in Australia as of September 2017 following the introduction of the Interactive Gambling Amendment Bill 2016, so for Australians the content on this page is informational in nature only. The information about online blackjack is intended exclusively for international readers.

Online blackjack games from leading developers like Microgaming and NetEnt are typically played with six to eight decks of cards, but with rules that are much more favourable to players than some of the sketchy rules being employed by land based casinos like The Crown. Playing online gives players the chance to choose from several 21 variants, including Single Deck Blackjack, so you can hand pick games with better house edges using the player friendly rules that you prefer.

Sign up at G’day Casino to claim your unlimited welcome bonus and choose between multiple blackjack variants using a different number of decks of cards.