Single Deck Blackjack

Single-Deck Blackjack is the game that started it all, and was such a strong game of chance from its very inception that the rudimentary aspects of the rules have remained largely the same. In the original game, or at least as far back as we understand the game, it was termed, ‘Ventiuna’ (twenty-one) in Spanish and vingt-et-un, literally, ‘Twenty-And-One,’ in French. Blackjack carries the same name in French to this very day.

The original object of the game of twenty-one is simply that there would be a player and a dealer, and both would attempt to draw cards to get as close as possible to twenty-one without going over. As they do now, aces counted as one or eleven, and the major difference was that the Spanish deck played a game lacking any eights or nines.

The game soon became widespread, and with only a few rule variations, developed into the popular casino game that we enjoy today. In fact, the Rules were actually adjusted in order to create a more player-favorable casino game as the dealer (or player to go second in a non-house banked game) would have a ridiculous advantage under the original rules. One of the early rule changes is that of the, ‘Natural,’ in that a player gets paid 3-to-2, (read: 1.5x the player’s bet) for a Natural Blackjack consisting of an Ace and Jack in the event the dealer doesn’t have one.

The original house banked game of Blackjack came to be called such because a hand with a, ‘Blackjack,’ was originally an extremely relevant hand. Any player who would be dealt a natural (with no dealer natural) consisting of an Ace and any black jack (spade or club) would receive a payout of 10-to-1. One can only imagine that card counters would love for that rule to still be in effect on single or double-deck games, but it didn’t last long.

Even though the Rule itself didn’t last long, both the name and the game did, and, ‘Blackjack,’ remains a casino staple and the best performing table game in the majority of casinos around the world to this day in terms of pure revenue.

The Rules:

There are a number of different ways that Blackjack can be played and one of the differences from one version of Blackjack to another is the number of decks that are used in the game. For the purposes of this article, we shall be discussing single-deck Blackjack.

The house must formulate a particular set of Rules with single-deck Blackjack because it is very easy for a player to have an edge right off the top if the house does not use a rule set designed for the game. The reason for that is because single-deck Blackjack gives the player an opportunity to play deck composition strategy. Deck composition strategy is essentially what card-counters do, but for single-deck Blackjack, one does not even have to be counting cards to occasionally have the opportunity to employ deck-composition strategy.

The first rule change we will look at is whether or not a dealer hits or stands on soft-17, which is any hand that adds up to seventeen with the Ace counting as eleven. In other words, A-6 would be an example of a Soft-17, A-2-4 is another example and A-2-2-2 is yet another. While it may seem that it is better for the dealer to stand if the hand total is seventeen (because the dealer is then allowed to stop hitting and no longer risks a bust) it is actually worse for the dealer to stand.

In order to understand why this would be, let’s just look at the possibilities of the very next card the dealer is going to take. Ignoring the player’s hand for a moment, let’s assume that a dealer has A-6 for a value of either soft-17 or a 7: When the dealer takes the next card, the following possibilities can occur with fifty cards left in the deck:

(15/50)-The dealer improves his hand to a 18-21 by way of another Ace, or a two, three or four. The four, of course, would give the dealer an unbeatable twenty-one that can only be matched for a push if it matches the player’s total.

(16/50)-The dealer draws a ten-card that results in a Hard-17, which is what the dealer would effectively have even if he stood on soft-17.

(19/50)-The dealer draws a five, six, seven, eight or nine, which are arguably the worst cards for the dealer because the hand is incomplete and busting is now possible. Even with that being the case, though, assuming the player plays perfect strategy based on the rules, the player will have a hand that beats (or pushes) seventeen enough of the time that the dealer is better running this risk.

The next rule that we must take a look at is the doubling rule, some casinos will allow a player to double on any two cards the player likes, whereas other casinos only allow doubling on hand totals of 9-11 and others still only allow doubling on hand totals of 10-11.

Whether or not a player can double on anything as opposed to 9-11 is really only relevant for single-deck games unless the player is counting and hits a really high positive count. In terms of a game being played, ‘Right off the top,’ single-deck is the only time a player would double a total of hard eight, and that would be against a dealer showing a five or a six. Obviously, the ability to double on anything also includes soft totals that do not otherwise equal 9-11.

That is actually a Basic Strategy example of where deck composition strategy comes into play. Think about this: If you are playing a single deck game the fact that you have a hand total of eight against a dealer’s five or six tells you a couple of things. First of all, if you had 4-4 for a hard eight you would actually split, which means that your hard eight must consist of 6-2, 5-3 or A-7 (which is actually considered a soft-18, but still a hand that you would want to double).

In the case of these hands, especially the 5-3, what is happening is the player knows that cards very good for the dealer’s five or six have been taken away. What the dealer would like to do is turn over a card that would give the dealer a hand total that makes it mathematically impossible for the dealer to bust when the dealer takes another card, or in the case of the player 6-2, removing a card that isn’t that bad for the dealer in the six.

In fact, in a single-deck game in which the dealer hits on soft-17, one of the only two card deck composition exceptions to Basic Strategy is that a player with a dealt 6-2 against a dealer six should no longer double down, but rather, should hit. The player would still double against a dealer five, however, because the six that the player has and the dealer cannot get (making a dealer total of eleven) is actually very good for the player.

A player might now ask, “Well, how much of a difference can the inability to double on a total of eight make, given that it must come up so rarely?” The answer is, quite frankly, a pretty dang big difference to the tune of roughly 0.146% House Edge if the player can only double on 9-11. That is also with the ability to double soft totals, of course. Will this extra 14.6 cents on every $100 really hurt a player? I guess it depends on how much the player plays, but remember, every change to the rules that is bad for the player adds up over time.

We must now look at the rule if the player is only permitted to double on hand totals of ten and eleven, this is an even worse rule for the player because there are even more doubling opportunities for the player with a hand total of nine than there are with eight. In single or double-deck Blackjack, Basic Strategy dictates that a player double a hand total of nine against any dealer showing 2-6, and that’s even true of games with four or more decks, with exception to doubling against a dealer showing a deuce.

Therefore, many doubling opportunities are lost if the player may only double on hand totals of ten or eleven, and the effect on the House Edge in a game where the dealer hits Soft-17 compared to being allowed to double on 9-11 is about 0.137% added to the House Edge. Compared to the game in which a player can double anything, the difference is .0276%.

For those of you who may wonder why the difference between going from double on anything to 9-11 is roughly the same as going from 9-11 to 10-11 only when there are so many more doubling opportunities on the nine, the reason is because that the eight v. dealer five and eight v. dealer six opportunities are incredibly strong because of deck composition. In fact, it is only because of the changes to deck composition in single and double deck that doubling a player nine against a dealer deuce is the correct play, the play is fundamentally so close to neutral (in terms of expected value) that in games with 4+ decks, the composition of a nine v. a dealer deuce is not enough to make doubling the superior decision, and the player would just hit.

(For the remainder of this article, we are going to assume that the dealer Hits on Soft-17 and that the doubling is limited to hand totals of 9-11)

Now that we have discussed doubling, we have to address splitting followed by the two together: Whether or not a player may double after a split.

The first question is to how many hands may a player split? For example, if the player is dealt a 4-4 (Hard 8) against a dealer six, then the player is supposed to split the fours and take a new card on each of the two fours in order to form two new hands. In some Blackjack games, the player has the opportunity to do this yet again if the player were to draw another four on one of the other hands, and then perhaps even again after that! This process is called, ‘Re-Splitting,’ and the ability to do so is a favorable rule for the player.

The difference in being able to split to a total of three hands (i.e. resplit once) between not being able to resplit is 0.01597% whereas the difference in being able to split to four total hands (resplit twice) rather than splitting only once is 0.01701%. While these may not seem like major differences to the house edge, remember that every little bit counts, the culmination of ALL of the rules is what generates the ultimate House Edge for the game, and most importantly, having more options (as a player) simply makes the game more fun to play!

The difference between being able to split to two, three or four total hands as relates the House Edge is actually more pronounced in games with multiple decks. The reason for that is because the deck composition is such that a player is more likely to get additional re-splitting opportunities the greater the number of decks there are. For example, imagine a hypothetical shoe consisting of 1,000,000 decks of cards: A player getting dealt a hand such as 4-4 and then resplitting and getting another four barely touches the probability of yet another four coming out with the very next card.

(For the remainder of this article, we will assume that the player is allowed to only split once to two total hands)

The next question relevant to the player is whether or not the player is permitted to double-after-splitting, and there is quite a variety of situations in which this becomes relevant! One example of a hand in which a player would want to be able to do so is a hand such as 4-4 against a Dealer six which is split and the player draws either a five, six or seven. (depending on what the rules are for what a player can double on, with the rules we are now using, all of those numbers would be relevant) In addition to having more hands with a positive expectation, the player has (in the case of a five against a dealer six or a six or five against a dealer five) pulled a card that is extremely good for the dealer. Of course, the dealer already has his/her card, so nothing can be done about what the card is, in fact, but the player makes decisions not knowing the dealer’s card.

In any event, if the player has the capacity to double after splitting, then the House Edge is reduced by about 0.1222% in favor of the player. This difference becomes slightly greater if the player could split to multiple hands because more hands means more potential opportunities to double after splitting.

Blackjack rules typically dictate that a player can only Split Aces once, and the rules that we are assuming for the remainder of this article do not allow re-splitting, so we shall discuss splitting Aces as if the rules did allow resplitting to a total of four hands. Resplitting Aces is advantageous for the player because, once split, aces can often not be hit upon or resplit, which means if you split two aces and draw another ace, you’re stuck with a twelve which is a horrendous hand total (though, effectively the same as a 13-16 if you can’t hit anyway). Splitting Aces is always a good idea because the player is (ignoring the dealer up card) 16/50 to make a twenty-one, 4/50 to make a twenty, 4/50 to make a nineteen, 4/50 to make an eighteen and 4/50 to make a seventeen. Alternatively, the player is only 18/50 to make a useless hand (16/50 if Aces can be resplit because drawing another ace is a positive).

Most games that allow resplitting do not allow for the resplitting of aces, but it happens sometimes. Furthermore, it’s a good mistake to look for should you play in a Brick-and-Mortar casino because many dealers will allow it, even though the House Rules technically say otherwise. The difference in the house edge if a player can resplit aces up to four hands on a single-deck game as opposed to not at all is 0.03216%. Again, this is a rule that will have a more pronounced effect on a game with more decks due to the composition dependence of the likelihood of the play.

The next rule we will address is whether or not a player can hit on Aces that have been split. For the purposes of this rule, we are going to go back to assuming that the player may not resplit in our single-deck game. The ability to hit Aces that have been split is an incredibly positive allowance for the player because it enables the player to take advantage of splitting Aces without worrying about any chance of being stuck on a bad (12-16) hand that cannot win unless the dealer busts. It also gives the player more doubling opportunities if the player is also allowed to double after splitting.

Essentially, what happens if the player is allowed to hit split Aces is that the player will not be stuck on hand totals of 12-16 after taking the card on each of the split Ace hands. In fact, the worst case scenario, if the player cannot resplit Aces, is that the player ends up drawing another Ace (Hard 12 total) as that is the only, ‘Hard,’ hand the player can end up with, and therefore, the only hand in which a third card (the hit) could potentially bust the player. Otherwise, every card on the split aces will either give the player a completed hand, or alternatively, the potential to take a hit to improve the hand with literally zero risk of busting.

Given all of our other rules, the ability to hit Split Aces (no resplitting) improves the game by 0.13011% House Edge for the player.

Another rule is the European, ‘No Hole Card,’ rule, and this is actually a rule that exists entirely on the dealer’s side, but it does impact a player’s decisions. With this rule, only the dealer’s upcard is known prior to the player acting, the dealer does not check for Blackjack before the player acts. If the player splits or doubles with this rule in place, the player will lose ALL wagers if the dealer ends up with a natural as opposed to the hole card rules that force the dealer to check for a natural before the player makes any decisions. There are a number of plays this influences in different ways, (in terms of the player needing to play more conservatively) but the biggest of these rules is that a player would no longer double a total of eleven against a dealer showing a Ten or Ace because the player has no way of knowing whether or not the dealer has a natural. With the hole card, ‘Peek,’ game, the dealer, ‘Peeks,’ and tells the player he/she does not have a natural hiding under there.

The difference in the House Edge between these two possibilities is 0.11249% with a dealer checking for blackjack being far more favorable for the player.

(For the remainder of this section, we will assume the dealer checks for Blackjack)

The next question is whether or not a player is allowed to Surrender, which means to forfeit his/her hand and receive half of his/her wager back if he/she does not like the hand. In a single-deck game in which the dealer checks for Blackjack, if allowed, the player would surrender any total of 15-17 against a Dealer Ace, a total of 16 against a dealer ten, and a 7-7 against a dealer ten or Ace. The difference in House Edge is 0.03801% if the player is allowed to Surrender given all of the other Rules with looked at.

The final rule that we will look at is Blackjack paying 6:5 rather than 3:2. If the game pays 6:5 on a player natural, do not play that game, enough said.

How Do the Rules Affect Me?

When it comes to the effects of the Rules, what I am going to do really quick is look at the most player-favorable set of rules for a single-deck game v. the most player unfavorable set of rules. I believe this will help everyone see how much of a difference the rules can make.


Dealer Stands on Soft 17
Double After Split: Yes
Double on: Anything
Resplit: Up to Four Hands
Resplit Aces: Yes
Hit Split Aces: Yes
Dealer Peeks: Yes
Surrender: Yes
Blackjack Pays: 3:2

With just Basic Strategy (as opposed to Optimal deck-composition strategy) the player advantage on this set of rules would be 0.22122%, which means that the player would make about twenty-two cents for every $100 bet over the long run. Let us compare that with the worst possible set of rules:

Dealer Hits Soft 17
Double After Split: No
Double: 10-11 Only
Resplit: No
Resplit Aces: N/A
Hit Split Aces: No
Dealer Peeks: No
Surrender: No

With all of that, the house edge with Basic Strategy would be 0.70768%, which would mean the player is expected to lose about 71 cents of every $100 bet. The overall difference between these two games is 0.92890%, nearly a full dollar per $100 bet difference. If we make Blackjack pay 6:5 on our bad rules, the House Edge goes up to 2.10245%, and even with our otherwise great rules, the player advantage turns into a house edge of 1.17355%.

Hopefully that teaches everyone about 6:5 Blackjack, 6:5 Blackjack making all of the other rules as good as possible for a single-deck blackjack game is still worse than 3:2 blackjack making all of the other rules as bad as possible for the player.


The number of decks that is used in a Blackjack game is a Rule in and of itself, and generally speaking, because of deck-composition strategy and decisions, the player bucks a lesser disadvantage by being able to play a game with fewer decks. That’s the good news.

The bad news is that there are still a number of other rules that can be changed in the game of Blackjack, so when deciding upon a blackjack game to play in a brick-and-mortar casino, it is important to understand not just the effect of the rules upon the house edge, but also how the rules might impact your strategy as a player. It is important to remember that the House Edge is only the House Edge if you are playing the game correctly, for example, if you always hit on a total of eighteen, what I call your, ‘Effective House Edge,’ would go up considerably!

Therefore, whether playing a game online or in a Brick-and-Mortar casino, it is important to compare the rules of one game to another, regardless of the number of decks, in order to determine what the best game for you is. For a card counter, however, this might be different as a double-deck game (with a slightly greater base house edge) might present a player with more frequent opportunities to make advantageous bets than an eight-deck game with a slightly lower, ‘Off-the-Top,’ house edge.

Either way, single deck Blackjack is, quite possibly, the most fun because it offers a wide array of situations and decisions that do not come up in most, and sometimes in any, other different variations of the game. Again, the reason for this is because there are more changes to the Basic/Optimal strategies of the game based on the varying effects of deck composition which can be impacted by just a few cards coming out.

Software Providers that have Single Deck Blackjack