Blackjack was originally only played with a single deck of cards, but after a time players found ways of exploiting this to their advantage, so casinos got wise and added more decks to the shoe to make life more difficult for wily players.
The number of decks used in a game of blackjack can be anything from one single deck up eight decks in most variations, although there is no hard and fast rule so technically even more could be used.
This does have an impact on the game because it effects the house edge, which in turn impacts your chances of winning, so it makes sense to understand a little bit about how this works.
Blackjack House Edge
The house edge in blackjack is very small indeed, around 0.5% if you play a classic version and use perfect strategy, so any change to it one way or the other is significant.
That said, with so many variations of the game using different rules or extra features it is almost impossible to talk about the house edge without generalising so that is what we will have to do here.
The number of decks being used will have an impact on the house edge because the more decks that are added the lower your chances of being dealt blackjack. That might not seem to make sense at first since it only affects the number of cards in the shoe, not the ratio, but look at this:
Imagine you are dealt an Ace in a single deck game.
There are now 51 cards left and sixteen of them are worth 10, which would give you blackjack.
You therefore have a 16/51 chance of getting blackjack which works out as 31.37%.
Now imagine you are in the same situation but in an 8 deck game.
You have an Ace so there are now 415 cards left in the shoe and 128 of them are worth 10, which would give you blackjack.
You therefore have a 128/415 chance of getting blackjack which works out as 30.84% – a drop of 0.53%.
You can see the impact the number of decks has on the house edge in the table below:
|Number of Decks||House Edge|
These are the most common deck numbers found, but there is no law saying a game can’t use 5 decks or 7. The table also assumes you are playing a perfect strategy, which basically means you are making the correct decision in any given scenario, mathematically speaking.
Players who do not use perfect strategy tend to give away 1.5% extra back to the house on average, bumping the edge up to around 2%. Every hand played incorrectly chips away at your chances and increases the casino’s house edge.
Blackjack is a game based on dependent events, so cards dealt in the past have a direct impact on the probability of what the next card might be. For example, if an Ace is dealt first in a single deck game there are only three left in the pack, so the chances of another coming up are slimmer.
Players got wise to this and some even came up with systems to track which cards had been used and which were still in the deck, thus giving them an advantage when deciding what action to take with their hand and what stakes to play.
This became known as card counting and it first surfaced in the 1950s, with a number of different methods being developed but all of them allowing the player to track the cards in some way.
When playing a single deck game it was incredibly easy for card counters to keep a count of the number of high or low cards left in the deck and then adjust their bet accordingly – so they would bet more when they had the advantage and less when they didn’t.
To combat this, casinos began to add more decks into the shoe, so in a real casino the number of decks used has a big impact on anyone trying to count cards. Card counting is not illegal but if you are suspected of doing it you may well be asked to leave.
Sadly, card counting is not possible online even if playing a single deck game. The game is built to shuffle the cards after each game, so you essentially start from scratch again on each game.
This would take forever in a real casino but takes no time at all online.
Questions About the Number of Decks Used in Blackjack
Can I Choose how Many Decks the Dealer Uses in Blackjack?
Unfortunately not, the terms are set by the house or by the game developers if playing online.
There is so much choice out there these days though that you can easily find the game you want with a quick search.
Why do Some Blackjack Games use More Decks than Others?
Extra decks were added to make life difficult for card counters as we know, but why then do some games still use a single deck?
It could simply be to attract more players in the hope that they then go on to play other games at the casino with a bigger house edge, and after all the casino is still set to win even with a smaller house edge.
Online, cards are automatically shuffled before each hand, so playing with a single deck only benefits the player up to a point.