Why does deck size matter in BlackJack?

When playing Blackjack, whether online or in a land-based casino, it is essential to know precisely what the odds are to give you a higher chance of winning.

Blackjack table with card games deck
Blackjack cards

Where Blackjack is concerned, it is all about ratios, and a good knowledge of these before you start playing can give you an advantage.

Today we delve into the number of decks that casinos use, which is also an important factor in how big chance we have of winning, when we play Blackjack.

Odds to get Blackjack in a single-deck game

Playing Blackjack in a single deck game will give you a better chance of winning, and using mathematics to explain should provide you with insight as to why.

This explanation is based on one person playing, however, the probabilities apply regardless of the number of players at the table.

1 card deck

The likelihood of getting an Ace in your first card is 4/52. You now need a card of the value of 10 to complete your blackjack.

16 cards can give you the 10 you need to complete your Blackjack.

These are the 10, the Jack, the Queen and the King of each suit. So the initial probability of drawing the Ace is 4/52 or simplified as 1/13.

That means the likelihood of drawing a card valued at 10 next is 16/51.

This is not calculated from 52 cards because an Ace has already been removed, so there are only 51 cards left in a single deck.

This means that the chance of getting a blackjack with one deck game is around 4.83%. We will now compare that with a two-deck game.

Odds to get Blackjack in a two deck game

As explained in the above description of the one deck game, the two deck variant is the same as we work it out by the number of cards left at any given time.

So if we look at drawing an Ace in a two deck game, the odds of that happening are 8/104, which still results in 1/13. It’s the next part that differs.

2 card deck

The amount of 10 valued cards will be 32 in two decks. This gives us a probability of 32/103 or 4.78% chance. We compare that to the 16/51 of the single deck or expand it to the equivalent of 32/102.

Although only a tiny difference, it shows a slightly higher chance of hitting blackjack more often in a single deck by 0.05%.

These odds continue to decrease as more decks are added to the shoe.

How many decks do online casinos use?

There is no set amount of decks that online casinos have to use. It is also worth remembering that it can differ between virtual games and live dealer games.

The live dealer games are predominantly for people who enjoy gambling online but want to feel that they are still betting in a brick-and-mortar casino.

They tend to mimic real casinos and use 8 decks. It tends to be between 6 and 8 decks for virtual games, but it can be common for a virtual game to use 1 deck.

If this happens, that deck is shuffled after every deal.

Top casinos to play at

How do I check how many decks they use at a table?

You can ask the dealer if you are playing in a land-based casino. They will have no problem providing that information.

Online casinos can be trickier. Some online casinos will state how many decks they use in the information tab. They are not required to tell you upfront.

You can check this information by using the online chat or any other customer care options they have and just asking them. They should provide you with accurate information.

One deck basic strategy explained

If you look at the chart here for one deck basic strategy, this will explain how the one deck basic strategy works.

It is also helpful to know that when the casino offers you the chance to take insurance, it is not always advisable.

This will happen when the dealer turns over an Ace on the first card. By accepting insurance, the house edge rises.

1 deck strategy basic

Two deck basic strategy explained

The chart for two-card basic strategy breaks down how best to use your cards with a two-deck strategy.

There are many free online blackjack games where you can test these theories and give yourself a better chance of winning.

2 deck basic strategy

More strategies explained

Blackjack is based on math, and some of the best and brightest have tried to break down the best odds of what to do depending on the value of the first two cards.

Whether to hit, stand, split or double down can be confusing at first, but the table below will give you an insight into the best action to take, depending on the probabilities.

View all Basic Strategy Blackjack charts here

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How many decks in Blackjack is best?

The fewer, the better. Less decks in play mean a higher probability of winning.

Can I choose a casino based on how many decks they use?

You can check different online casinos to see if they publicise how many decks they use. Alternatively, you can use internet search engines to check if there are any casinos that operate a specific number of decks.

Are my odds better online or in land based casinos?

Online casinos tend to offer more favourable payouts or bonuses for players. It will also be easier to find lower deck games online.

Online casinos can also shuffle after every deal.

A land based casino will not do this, which can mean that the odds will be better at land based casinos depending on what cards and how many have been dealt before the shuffle.