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Blackjack odds explained

Blackjack odds explained


Blackjack is, in every sense, a numbers game.


Of course, the only number that really matters is 21 in this ancient card game beloved by casino fanatics, but there are plenty of other digits that go into blackjack success.


Do you know the win probability of your hand?


Do you know the win probability of the dealer’s hand?


Do you know the likelihood of drawing an ace, or any other card, next?


What is the house edge?


The good news is that you don’t need to be a mathematician or an accountant to succeed at blackjack! However, you will need a basic appreciation of numbers for one good reason: calculating blackjack odds.


Once you understand the blackjack odds and payouts, you can make your decisions on whether to hit, stay or double down based upon simple mathematical theory – rather than instinct or other human emotions that are – let’s face it – unreliable at the best of times.


To be a strong blackjack player, you need to know what to do in any scenario that presents itself at the table. This decision-making is made easier and more profitable when you understand the odds of what’s in front of you. 


In this guide, we’re going to walk you through everything you need to know about blackjack odds, from how to read and calculate them to using them in your favor. 


By the end, you will be armed with the tools that all good blackjack players need in their mission to lower the house’s edge and to secure long-term profitability from their play. We will answer the question, what are blackjack odds? And you will know how to interpret these in your play.


The basics of blackjack odds


The majority of casino games are solely based on luck. Spin the slot reels or the roulette wheel and your chances of winning are completely out of your hands.


However, in blackjack, skill and nous are two key features. Sure, you could use some luck – it’s always great to be dealt 21 straight away – but by utilizing some basic concepts, you can actually decrease the house’s edge – hence why we can say with some confidence that blackjack is a game of skill.


Key to this is understanding the odds for blackjack. Did you know that you can calculate the odds of an ace (or the card you need to make 21) being dealt next?


Did you know that you can calculate the odds of the dealer busting their hand based on their upturned card?


You can also calculate the effect on the house’s edge when a particular card is removed from the deck – and while this gets complicated in multi-deck games, for single-deck blackjack, this is another amazing weapon to have in your armory.


In this guide, we’ll show you how to calculate the blackjack odds of winning for each hand and combination. You’ll learn:


  • When to hit
  • When to stand
  • When to double down
  • When to attack the dealer’s hand
  • How to lower the house edge


Spoiler alert: there is no ‘silver bullet’ that guarantees blackjack success. In the end, you are still relying on being dealt strong cards.


Remember, the house always wins because, thanks to the law of large numbers and their in-built edge, more players will lose at blackjack than will win. However, knowing the blackjack odds of hitting on 16 or winning with 18 will increase your chances of being in the former category greatly.


In this article, we will show you how.


How are blackjack odds calculated?


The great news is that you can calculate the probability of many different things happening at the blackjack table.


To kick things off, let’s do some simple math as a warm-up. We know that there are four aces in a standard deck of cards, and in that deck, there are 52 cards in total. Therefore, we can divide 52 by four to work out the probability of an ace being the first card drawn – that’s a one in 13 chance, or 7.69% to be exact.


We can also calculate the likelihood of an ace appearing after the game has started. Let’s say that four cards are dealt but none of them are aces. This means that the calculation is now 48 cards divided by four aces – our percentage increases to 8.33%.


This is just one example of how we can use probabilities and odds to determine our chance of drawing any particular card in a given scenario.


Of course, the math gets harder in multi-deck blackjack games, but this is not to say that it can’t be done – you just need to work out how many cards in total are in the shoe so that you can begin your calculations.


We can also use these blackjack odds vs house to calculate a theoretical win percentage. Let’s say that you have drawn 16 (nine and seven) in the first round of a single-deck blackjack game. You want to hit again but are worried about going bust. The dealer’s upturned card is a 10, but, of course, we can’t see their other card – let’s assume that it’s a five or below to manage our risk.


We know that we need a card valued at five or less to improve our win probability. We can work out the math – four cards are on the table, leaving 48 left in the deck, and we’re assuming that one of our target cards is in the dealer’s hand.


So, there are 4x aces, ones, twos, threes, fours and fives, minus the one card we’re using as our buffer. In total, 24 cards can improve our hand (without busting) from the 48 available, so we have a 50% chance of hitting the number we want.


It’s also worth knowing your chance of busting if you hit with a certain value of hand. If you have a score of 11, you can’t go bust by hitting another card – that’s a given. If you have 12, your probability goes up to 31%, and for 14, you have less than a one-in-two chance of success (56%). 


If you have a score of 19 and hit, your chance of busting is 85%. And for scores of 20, this goes up to 92%. Don’t do it!


Later in this article, we will show you how to calculate the change to the house edge when a certain card appears, how your win ratio alters based upon the dealer’s upturned card, and so on.


For now, though, we just wanted to illustrate how, with some fairly straightforward math, you can calculate on the spot what kind of a position you are in with a particular hand. 


Blackjack odds house edge


The easiest way to explain the house edge is with another casino favorite: roulette.


Imagine that a roulette wheel only featured the numbers 1 to 36, with only red and black pockets.


The main bets placed – odd or even, red or black – would be 50/50. So, whether the player is profitable or not will be all down to luck.


The casino is able to protect against that scenario with the introduction of the zero pocket, or the double zero in the case of American roulette. If the ball lands here, all wagers are lost – unless you’ve bet on zero, of course.


The probability of spinning a zero is around 2.70%, and so you can see how a casino is able to lock in a profit thanks to the law of large numbers – across 1,000 spins, the zero will be spun enough times to turn the game in the casino’s favor – the ‘house edge’ as it’s known.


There is also a house edge in blackjack, and that’s for one simple reason: the player has to complete their hand first.


There will be many instances where the player busts and the dealer hasn’t had to do a single thing – this occurs in around 28% of cases. This is free money for the house. 


Also, if you stand on 17, let’s say, then the dealer’s decisions are made for them – that’s the target they go for. It’s why there can be ‘bad beats’ in blackjack when a dealer improbably deals themselves a low card to beat your standing position.


All things considered, the house has an edge of around 8% in a standard blackjack game, but there are ways that we can reduce this.


Counting cards is one option, but that is not exactly advisable – it’s not illegal, but in a land-based casino, you may get thrown out if you get caught. Also, in online blackjack with multiple decks, counting cards is a very difficult task indeed.


Instead, we point you towards more organic tactics, such as blackjack basic strategy (sometimes known as perfect strategy). This is a table that details the move you should make in any given opportunity based on theoretical probability.


As a consequence, we urge you to use basic strategy in your play – there are stacks of resources online to assist you, including a blackjack odds cheat sheet.


In the meantime, here’s a look at what happens to the casino’s blackjack odds house edge when a certain card is removed from a single deck:


  • 2 – -0.40%
  • 3 – -0.43%
  • 4 – -0.52%
  • 5 – -0.67%
  • 6 – -0.45%
  • 7 – -0.30%
  • 8 – -0.01%
  • 9 – +0.15%
  • 10 – +0.51%
  • J – +0.51%
  • Q – +0.51%
  • K – +0.51%
  • A – +0.59%


This is an interesting visual of how each card being taken out of the deck affects the house edge.


Knowing these numbers, and applying basic strategy, means that you can lower the house’s edge – playing in this tactical manner is the key to long-term success in the game.


Players’ advantage in blackjack


So, how can you reduce the house’s edge?


We’ve already mentioned playing with basic strategy, and to reiterate, we implore you to follow these proven methods of statistically increasing your chances of winning a hand – and thus decreasing the casino’s advantage.


You will notice that the perfect blackjack odds chart calls for you to double down with various combinations in hand, and it is the doubling option that is crucial in helping you to lower the house edge.


For example, when there are lots of high cards left in the deck and you are dealt 11, the percentage play is to double down – there is a decent chance that you will hit 21, or close to it, with the cards available. Remember, doubling down also doubles your stake – but also therefore increases your winnings.


The option to split pairs is also an advantage to players that the dealer does not have. Splitting can create two winning hands, and it certainly increases your chances of being successful with at least one of them.


The blackjack odds with perfect strategy can – with most variants – reduce the house’s edge to less than 1%, which is an almost level playing field. You can’t say fairer than that!


You will still need two key factors in order to be successful: luck and discipline.


Even when playing perfect strategy to a tee, you still need good cards in order to maximize your hands – it’s very difficult to ‘make a silk purse from a sow’s ear’, as the old expression goes.


For the strategy to be implemented perfectly, you will need to retain discipline in the face of bad beats and losing streaks, knowing that, in time, such runs will be reversed given the law of large numbers.


Unlucky players will be able to turn around losing streaks if they stick to the principles of basic blackjack strategy. Ill-disciplined players running on tilt and ignoring the techniques required simply will not be able to turn around a losing session.


We have written about card counting. This is a controversial topic and one that needs plenty of careful consideration, and there are reasons why you may want to avoid this – especially if you are new to the game.


However, does counting cards in blackjack really work? It certainly can hand you an advantage, and if you want to pursue this avenue, there is lots of information available online – the high/low system tends to be the most productive. 


Why odds are important in blackjack


If you’ve read this article up until this point, you will already have a fair understanding of why the odds are so important in blackjack.


Making the percentage play, rather than relying on gut instinct and feelings, is essential to your long-term success at the table, and an underlying understanding of the odds and probabilities involved is central to that.


One of the errors that blackjack players of all experience levels make is to focus solely on their own hand – i.e. what are the odds of blackjack being dealt, or at least standing on a competitive total in the late teens?


However, it is imperative that you also consider the dealer’s hand, because their chances of busting may be high based upon their upturned card – rendering the quality of your hand slightly less important. In short, you could win with a pretty iffy hand based upon the dealer’s misfortune. 


Here’s another fun set of odds that will improve your blackjack play – the blackjack odds of the dealer busting based on their upturned card:


  • 2 – 35.3%
  • 3 – 37.6%
  • 4 – 40.3%
  • 5 – 42.9%
  • 6 – 42.1%
  • 7 – 26%
  • 8 – 23.9%
  • 9 – 23.3%
  • 10 – 21.4%
  • A – 11.7%


As you can see, the chances of the dealer going bust are much higher when they have those ‘middling’ cards of 4 to 6 rather than an ace or a 10. Again, this is useful information to have at your disposal when plotting how to play your hand.


When do blackjack odds change?


It’s worth remembering that perfect strategy, and those ‘dealer bust’ probabilities, are the same in all forms of blackjack.


However, there are some differences when playing single deck from the blackjack odds with eight decks, and these do tilt the odds slightly based on what has gone before. For every deck added, the house edge increases exponentially – so the blackjack odds with four decks are less agreeable than single-deck games.


Indeed, the house edge in an eight-deck game increases by some 0.61% compared to single deck – in the context of long-term profitability, this is quite a percentage.


The presence of other players at the table is also interesting. More players means more cards used, and it actually becomes easier to track how many high cards are left in the shoe as a result. So, are blackjack odds better with more players? You could argue that they are.


Multiple decks in play certainly makes it difficult to count cards, and, of course, the action tends to go on longer before a shuffle is made – meaning that random results can be experienced with so many of each card value in the shoe. 


There are different variations of blackjack that offer unique rules, and so the odds will also vary in these cases. You may be wondering, what blackjack has the best odds? Blackjack Surrender, for example, lets you ‘fold’ a weak opening hand for the loss of half of your stake – this can be an excellent way of protecting your bankroll.


The odds vary when we talk about soft and hard hands, and specifically the ‘soft 17’ rule. Basically, at some casinos, the dealer has to stand on a soft 17 (a soft hand is one with an ace in it), and at others they don’t. So, it’s worth perusing the blackjack odds and rules of your particular casino to see where they stand on this topic. 


These are just some of the reasons why the blackjack odds can vary, but as we know, there are ways and means of reducing the house’s edge through our play regardless. The main focus is on attempting to stack the odds in your favor as best as possible – that’s the real secret to success in blackjack.

Blackjack odds explained



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