The Effects of Number of Decks on House Edge

Blackjack School

The game of blackjack is played all over the world in land-based and online casinos. It is considered the most popular game in the world after poker and the most popular banker’s card game (a game that is played against the casino/bank and not against other players).

Over the past couple of centuries as blackjack spread around the world, games inventors and casino operators started to change some of the rules and conditions of the game. Some of these changes have been in favor of players, while others favored the house by increasing the house edge.

Blackjack House Edge

When playing blackjack the player must always remember that they are at a disadvantage against the casino. There are several factors that put the casino at an advantage over the player but the main one has to be that when a player busts out of the hand they always lose their bet regardless of how the dealer’s hand performs. The dealer can also bust but as the player’s hand is played before the dealer’s hand, the player’s bet will be taken away from them as soon as they bust.

Regardless of this, blackjack is considered to be a very player-friendly game that offers a very low house edge and a high payout percentage for the player. The reason for this is that blackjack is not just a game of chance but also a game of skill, so when players apply basic blackjack strategy they lower the house edge to lower than 1% on most blackjack variations.

Number of Decks in Play

In most blackjack variations there is a direct effect of the number of decks in use on the house edge. Some blackjack variations have a fixed number of decks in use as the use of any other number of decks would not sit well with some of the rules.

However many blackjack versions can be played using different number of decks. The change in the number of decks in use has a direct effect on the house edge and can lower or increase it, depending on the number of decks in use.

In general the fewer decks are used, the lower is the house edge and vice versa. The fewer decks are in play the higher is the payout percentage the player can expect from the game when playing optimally using basic blackjack strategy.

Why Number of Decks Matters

The reason that the number of decks has such an effect on the house edge as that the number of decks has a direct effect on the player’s chances of hitting a natural blackjack.

The main reason for this is that when fewer decks are in use and the player is dealt a 10 valued card as their first card, there is a higher probability of the second card dealt to the player being an ace which will result in the player having a natural blackjack.

In addition there is a lower chance of the dealer having a natural blackjack against the player’s natural blackjack. Such a hand will result in a tie and the player’s bet will be pushed (returned to the player).

The Real Percentages

Let us take for example a fixed set of rules and see how the house edge changes the more decks are in play.

The Rules:

  • Double on any two cards
  • Dealer hits soft 17
  • Double after split allowed
  • Resplit up to 4 hands
  • No Surrender
  • No hitting split aces
  • Player’s original bet only lost when dealer showing blackjack
  • A cut-card is in use
Below is a table that lists the house edge that corresponds to the number of decks in use when playing by the blackjack rules listed above:

No. of Decks in Play House Edge
Single Deck 0.17%
Double Deck 0.46%
Four Decks 0.60%
Six Decks 0.64%
Eight Decks 0.66%

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