How Does the Number of Decks in Blackjack Impact the House Edge

How Does the Number of Decks in Blackjack Impact the House Edge?

How Does the Number of Decks in Blackjack Impact the House Edge

Blackjack is consistently ranked as one of the most popular table games at casinos worldwide, regardless of whether the establishment is physical or virtual. It doesn’t matter how you play blackjack; there are a lot of subtle differences in the gameplay that can significantly impact the return to player (RTP) rate, and the number of decks used is one of the simplest to comprehend.

The RTP is essentially a breakdown of how much money a player can anticipate losing on average while participating in a particular casino game. Every game in the casino has some house edge or profit, which is how the establishment makes money. The return on investment (RTP) is typically presented as a percentage and can change by a sizeable margin. According to the UK Gambling Commission, there is no statutory minimum percentage payout for a gaming machine. The RTP (return to player) on some slot machines can be as low as 80%, which means that a player can anticipate getting back only 80 pence for every pound wagered throughout their play.

When it comes to games in which the outcomes depend solely on random chance, the average is typically determined using at least 100,000 spins. However, this is just an estimate. Other casino games, such as roulette and blackjack, each have their unique house advantage (also known as RTP), which is determined by the underlying mathematics of the game.

For the roulette game, for instance, there are 37 slots on a standard UK wheel. The payout for any given number is 35 to 1, so we can say that, in theory, if you place 37 individual bets of £1 on a single number, you would expect one of those bets to win, which would result in you having £36 remaining despite having begun with £37. This results in return to player rate (RTP) of 97.3% and the actual RTP for the roulette game. This translates to a gambling margin of 2.7%.

Optimal Gaming

In the blackjack game, the idea of “optimal play” was developed through a process that involved intricate mathematical computations and a profound comprehension of the game itself. This indicates that regardless of the player’s card and the dealer’s card, there is always a single strategy that, over the duration of the game, will produce the most favorable outcomes for the player.

The RTP is determined based on a player’s optimal strategy when playing blackjack. If a player deviates from this strategy in any way, the RTP will decrease, resulting in larger losses for the player and larger margins for the house. Assuming that the player is performing at their absolute best, the RTP in blackjack depends on the specific rules being played, and various factors can affect this.

Blackjack is one of the most popular table games offered at online casinos, and the house edge for this game typically ranges from 0.4% to 1.5%. However, it can go a little lower under the rules of the most liberal casinos, and it can go a lot higher at less generous casinos and tilt the rules in their favor. The house advantage is significantly influenced, to a large extent, by the number of decks that are used, as well as by a number of other variables, which include the following:

  • If the dealer chooses to strike on soft 17, the return to player percentage will be lower.
  • Player permitted to double after a split – if yes, this increases the RTP
  • Participants can double on any first cards – if so, this also increases the RTP
  • Aces that are divided – the RTP is higher if the player can split aces.
  • Blackjack payouts of 6/5 rather than 3/2 are uncommon these days; however, lesser BJ odds significantly reduce RTP.

How Significant Is the Effect of Using Multiple Decks?

Adding more decks has a big influence, probably a far greater one than most players are aware of at this point. If we assume fairly standard but still rather liberal rules in the other areas that matter, including those listed above, we can see the impact of adding more decks below. Note that the house edge, often known as the casino’s margin, is displayed in this table rather than the RTP. Although having a high RTP is desirable, everybody who enjoys playing blackjack wants the house edge to be as small as feasible.


Although this may not appear to be a significant issue at first glance, even slight percentage variations can substantially impact over time. When going from a game with one deck to one with two, there is a significant increase in the house advantage; in fact, it is very close to quadrupling when moving from a game with one deck to one with two. Blackjack is a game in which players may play hundreds or even thousands of hands, and even with low stakes, such differences quickly add up.

This will be of particular interest to you if you are playing blackjack to satisfy the bonus wagering requirements of an offer, as that is the scenario in which you will most likely be doing so. Blackjack has a return-to-player percentage significantly higher than virtually every other game available (video poker can beat it depending on what rule variations are used in both games). Consequently, it is a well-liked option for players who are wagering bonus funds and want to try to ensure that they will still have some “free” cash remaining after completing the wagering requirements.

Most online casinos became aware of this fact quite a few years ago. As a result, many do not count blackjack wagers toward the requirements for receiving bonuses or only count blackjack wagers at a reduced rate. For example, a bet of ten pounds might only lessen the need for rolling over the bonus by one pound. Despite this, if you are trying to clear a prize or are just playing for fun, the best bet you can make is to choose the blackjack variation in which there are the fewest decks in play. This is true even if the other rules are the same.

Numerous online casinos provide players access to a comprehensive selection of blackjack games and variations, including an increasing number of fresh and innovative takes on this time-honored card game. However, in most cases, the most straightforward variations of the game offer the highest return to player (RTP) percentages. This is true even if the possibility of winning larger sums of money or enticing add-ons is what initially draws your attention to the game. All online gambling sites do not offer single-deck blackjack; however, if you can find one that does, it is highly recommended that you play this version of the game.

Why is it that having more decks is bad for the player?

We have established that playing blackjack with multiple decks will have a negative impact on your results over the long term; however, the question remains as to why this is the case. The increased possibility of being dealt a blackjack is one of the contributors, which may be the most important. Well, it’s a combination of a few different factors.

Let’s say you play a single hand, and the first card dealt to you is an ace. There are 16 face cards or 10s out of the remaining 51 cards, which means your chance of getting a blackjack is 16/51, or 31.373%. When played with two decks, this number becomes 32/103, which equates to a probability of 31.068%. This only seems like a small difference, but it has a notable impact, and while the same applies to the dealer’s chance of getting blackjack, while you will be paid at 3/2 odds, they will receive just your stake. In addition to this, the likelihood of a blackjack push, which occurs when both you and the dealer get a blackjack, is significantly diminished.

Similar calculations and theories can be applied to other potentially profitable situations for the player, such as when holding a good two-card combination that can be doubled, such as a 7 and 4 or a 6 and 5 example. To return to the game of blackjack for a moment, not only does the player have a greater chance of getting a natural if their first card is an ace, but the same is true if their first card is a 10.

However, as we have established, the only circumstance in which the benefits of using a single deck are guaranteed to be realized are those in which no other playing conditions differ. Some online and offline casinos offer a reduced payout of 6/5 for blackjack in their single-deck games. This can be frustrating for blackjack players. Let us add a third column to the table we were using to demonstrate how making that seemingly insignificant change causes the house edge to increase while simultaneously causing the return-to-player percentage to decrease.


The table demonstrates that lowering the blackjack chances has a far higher impact than increasing the number of decks in play. So, even if someone gives you the advice to “always play with a single deck,” it is extremely important to check that all other important rules are also followed.

If you play a blackjack game with one deck and the payoff is decreased to 6/5, the house edge is approximately 1.5 times higher than if you played a game with eight decks and the standard odds of 3/2. Playing a game with as few decks as possible is an excellent strategy, but it is by no means the only thing to consider.

The Use of Fewer Decks and Card Counting

With fewer decks, card counting becomes simpler and more effective. This strategy, which is covered in more detail in another post, will only be utilized by some players. The use of multiple decks does, however, make things more difficult for players who count cards, which is one of the reasons that casinos began offering multideck games in the first place.