Online Blackjack Rule Differences


Before we get into addressing the effects of different Rules, the first thing that we should do is come up with a baseline, and I am going to call that baseline, ‘Amazing Blackjack Game,’ and in the Amazing Blackjack Game, here are the Rules:

Decks: 1
Soft 17: Dealer Stands
Double After Split: Yes
Double: Any Two
Resplit: Up to Four Hands
Resplit Aces: Yes
Hit Split Aces: Yes
Player Loses Original Bet Only After Dealer BJ: Yes
Surrender: Late
Blackjack: 3:2

This awesome set of rules yields a player advantage of 0.37292% playing Optimal deck composition strategy. Of course, for this reason, you are likely never going to see such a set of Rules. However, this set of rules does provide a good baseline for the possible effects of changing any one of these rules.

The first rule that we will address is splitting. Splitting is a pretty standard allowance on most Blackjack games with the only real question being: How many hands can a player split to? We will address that question later on in this.

For the time being, we are going to look at Playtech Blackjack and we will first notice that Playtech Blackjack allows a player to split their initial two cards for every single game, however, the player may not split to more than two total hands:

Even the worst Blackjack games, which can be found on some bartop and other Video Blackjack machines around the country, generally allow a player to split, so common is the allowance. These machines are so bad, in terms of house edge, that many of them only pay even money on a player natural when the dealer does not have a natural, yet they still allow a player to split, so common is the rule.

The way that splitting works is that if a player is dealt two cards of like value, the player may then choose to use each of the two cards as the first card of a new hand by placing the amount of his wager once again to turn the one hand into two. In simple terms, the goal of splitting can either be one of two things, a player may try to make two good hands (or better hands) in order to take advantage of a weak dealer upcard, or alternatively, the player may turn one hand into two (such as splitting 8’s against a ten card) because the overall expected loss of two hands that each begin with that card against a strong dealer card is lesser than standing on the sum of the original two starting cards.

In other words, not being able to split at all would have a devastating effect on the player, however, it is practically unheard of for a player not to be allowed to split at all, so with that we will move on and determine what effect it would have on our game to be allowed to split to fewer hands.


If the player is allowed to only split to three hands, which is rare as it is usually two or four total hands, the effect on the house edge is negligible for our single deck game for a couple of reasons: First of all, it is a situation that does not come up that much in general to split to four hands, and secondly, the effect-of-removal of a certain card from the game (such as an eight) is such that it is considerably less likely that a player will draw another eight (or two of them) in a single deck game as opposed to a game with multiple decks.

In the case of our Awesome Blackjack Game, the player edge goes to 0.36962% when we only allow the player to split to three total hands, which is a difference of .0033%. The effect is greater, however, when we keep the same rules otherwise and look at an eight-deck game, because the player is more likely to be able to split to four hands if the player has the ability to do so. When we look at the house edge of Awesome Blackjack Game with eight decks, and otherwise the same rules, there is a House Edge of .10479% with the Optimal Strategy, but that House Edge is increased to .12311%, a difference of .01832% simply because the player is losing more opportunities to split to four hands as opposed to three.

In other words, when it comes to being able to split multiple times, the rule is more beneficial (from a house edge standpoint) on a game with multiple decks than it is on a single deck game simply because there will be more opportunities to split in such a fashion.

If we take a look at the single-deck version of Awesome Blackjack Game, and change the splitting rule to reflect a maximum of two hands, then we are left with a player edge of .31627% with Optimal Play, which is a difference of .05665% from being able to split to four hands. Once again, the difference is even greater on an eight-deck game because a player who can only split to two hands faces a house edge of .22011%, which is a difference of .11532% compared to being able to split up to four hands. Once again, the reason for this disparity is the fact that a player will be presented with more opportunities to resplit because there are more of that value cards (as a percentage) relative to the remaining shoe composition in a game with multiple decks.

In order to give a real world example, let’s suggest that a player gets dealt two eights for sixteen against a dealer ten. A starting hand of sixteen against a dealer ten would be a surrender for any hard 16 under these rules with exception to splitting the eights, which the player should always do. Now, if the player splits the eights against the dealer ten, and can only split once, and one of the hands draws another eight, the player is stuck with a hand totalling sixteen. At this point, the player must hit and will more than likely bust on that hand.

Let’s take a look at this with a single deck and eight decks:

With a single deck, there are 52 cards, so if we know the player has two eights and the dealer has a ten, then we know that only two of the remaining 49 cards in the deck are eights. As a result, the probability of the two new hands (starting with an eight) getting another eight is as follows:

First Hand: 2/49 = 0.04081632653

Second Hand No Eight on First: 2/48 = 0.04166666666

Second Hand Eight on First: 1/48 = 0.02083333333

Therefore, the probability of getting an eight on both hands is about 0.00085034013 while the probability of getting an eight on either one hand or the other is 0.08163265306.

However, when we take a look at getting two eights in an eight-deck game, in which there are 32 total eights to start with and 416 total cards would leave 30 eights and 413 unknown cards if the dealer has a ten. Thus, let’s take a look at the probability of drawing another eight now:

First Hand: 30/413 = 0.07263922518

Second Hand (No Eight on First Hand): 30/412 = 0.07281553398

Second Hand Eight on First: 29/412 = 0.07038834951

Both Hands: 0.07263922518 * 0.07038834951 = 0.00511295517

Therefore, the probability of getting an eight on both hands is .00511295517 while the probability of getting it on one hand or the other is 0.13791461952, so the likelihood of getting stuck with a sixteen when you can only split once is far greater than it would be with a single deck game. It is for that reason that, given more decks, the ability to split to fewer hands results in a greater detriment to the House Edge for the player.

Playtech does not have any Blackjack games, according to the Wizard of Odds review, that allow a player to split more than once. However, Microgaming and Realtime Gaming both do, but the Realtime Gaming versions come with other rule changes that amount to a greater house edge against the player than with the Playtech versions of the game. The Realtime Blackjack has a house edge in excess of 0.5%, which by my standard for online Blackjack, is an awful game.

Re-Splitting Aces & Hit Split Aces

Re-Splitting Aces is an interesting rule variation because, obviously, in order for it to apply the player has to be able to split to multiple hands in the first place. Most casinos do not allow the player to Re-Split aces, even when the casino would otherwise allow a player to split to multiple hands.

In fact, many Blackjack rules will not even permit the player to hit split aces, so the player is splitting Aces in that event and it is essentially be treated as a double down, in that the player is stuck only getting one card.

When a casino allows a player to draw to split aces, there will usually be some rule that compensates for that allowance in one way or another. For instance, with Microgaming Software, there are four blackjack games in which the player is allowed to hit to split aces (though none where the player can re-split aces) and those four games are four out of their five worst games in terms of House Edge. The way Microgaming compensates for the allowance is by restricting doubling to 9-11 only and restrict splitting to only one hand.

If we take a look at our, ‘Awesome Blackjack Game,’ we can take a look at the difference that not being able to resplit aces has on single deck v. eight decks:

Single Deck: New Player Edge .34604%, difference .02688%.

Eight Decks: New House Edge: .16529%, difference .06050%

Once again, the reason that this has a greater effect on the player in a multi-deck game is simply because the player is much more likely not just to have the opportunity to resplit aces, but also to have the pair of aces to split in the first place in the double-deck game due to the stronger effect-of-removal in the single deck game.

When we take a look at our game and eliminate the ability to hit split aces, here is what we come up with:

Single Deck: New Player Edge .23719%, difference .13573%

Eight Decks: New House Edge .2847%, difference .17991%

Again, the reason for the disparity in how it swings the edge of the game to the house is simply because a player is more likely to start out with a a pair of aces to split in the first place in an eight deck game. Since we do not know the card of the dealer ahead of time, we can take a look at the probability of being dealt a pair of aces given that we do not know what either of the cards will be:

Single Deck: (4/52 * 3/51) = 0.00452488687

Eight Decks: (32/416 * 31/415) = 0.00574606116

Therefore, we can see that it is a situation that comes up a bit more frequently in the eight deck game, and as a result, having no option other than to just split and take another card is something that affects the eight deck game more frequently as a result.

Doubling Down

Another rule that can come into play frequently for both online and live Blackjack is with respect to how double downs are treated. Doubling down is a function by which the player (you guessed it) doubles his or her bet, in exchange, the player may only take one card so absent the ability to double down, the player may end up with a hand that would have otherwise called for another hit.

The main difference between doubling down and splitting is the fact that doubling down is something that a player would only do when the player has the advantage in a hand. As with the example mentioned earlier, players will sometimes split in order to at least make a bad hand less disadvantageous. With doubling down, the player already has the best of the situation.

Virtually all Blackjack games offer the player the ability to double down, however, some games may restrict doubling down to hand totals of 9-11, while other games will restrict doubling down to hand totals of 10-11. While that may not seem like a huge deal, it certainly is because it can often be advantageous to double on, ‘Soft,’ (with an ace) total hands in excess of eleven, and alternatively, it is advantageous to double on a hard nine total against a 2-6 (or 3-6 if there are four or more decks) and in a single-deck game, a player will also double a hard eight against a dealer showing a five or a six due to the change in deck composition.

The first thing that we will look at is the difference in a single deck game under our, ‘Awesome Blackjack Game,’ rules when we restrict doubling, and then we will compare that to what happens in an eight deck game.

Remember that the player edge of, ‘Awesome Blackjack Game,’ is .37292%. We will now see what happens when we switch the doubling rules to 9-11 and 10-11, respectively.

9-11: Player edge of .21744%, difference of .15548%

10-11: Player edge of .06936%, difference of .30356%

Remember that, ‘Awesome Blackjack Game,’ has a House Edge of .10479% with eight decks.

9-11: House Edge of .20676%, difference of .10197%

10-11: House Edge of .30048%, difference of .19569%

What we can see here is that the differences are more substantial with the single deck game when we change the rules that they are with the game of multiple decks. The reason for that is the same as why the splitting rule changes are less detrimental to the player when it comes to fewer decks, and that is because of the effect-of-removal.

To wit, in the single deck game when we change those rules, all of the situations under which it is advantageous to double on a hard eight are taken away on 9-11, and all of those situations in which it is advantageous to double on a hard nine are taken away in 10-11. Additionally, the player loses the ability to double down on many of those soft totals.

With respect to the game with eight decks, it is true that the player still loses the ability to double on all of those soft hand totals, but there are fewer of them upon which the player would actually double. For just one example, the player would double a soft 12-16 against a dealer four, five or six in a single deck game whereas the player would not double a soft 12-13 against a dealer showing a four in a game of four or more decks…In fact, the player wouldn’t even make that double in a two-deck game.

Furthermore, the player never doubles a hard eight in a game with two or more decks and does not double a nine against a deuce in a game of four or more decks.

The result is that taking away opportunities to double by restricting the hand totals upon which the player is allowed to double has a greater effect on the house edge of a single deck game than it does on a multi-deck game due to the effect of removal on the single deck game making the player more likely to win in certain situations, and as a result, causing situations in which it is the correct decision to double that are not the case in other games.

Either way, just because a casino chooses to restrict doubling does not necessarily make a Blackjack game a bad one, compared to others, because it really depends on what the other rules of the game are. For example our, ‘Awesome Blackjack Game,’ based on only being allowed to double on 10-11 but keeping all of the other rules the same, would still be considered a quite good Blackjack game.

That is where it is important to say that it is the combination of the set of rules that leads to the house edge being derived, and with respect to that combination of rules, one rule is not necessarily going to make a game a bad one. For that reason, it is very important to look at all of the rules of a blackjack game and use a house edge calculator.

In order to determine whether or not a particular blackjack game is any good. For example, Microgaming’s best listed game on Wizard’s review is Vegas Single Deck, which restricts doubling to hand totals of 9-11.

The ability to double on certain hands, however, might make the game more fun for the player, so my advice to seek out a game if liberal doubling is important to you is to look for a game that fits that criteria and still has a house edge in keeping with the other games out there. For my part, I only like playing single or double deck games, not because I am a card counter, but because I LOVE getting to double an eleven against a dealer Ace!

Double After Split

This is obviously a combination of splitting and doubling by which a player may be allowed to split to multiple hands, and then place a double down bet on one or more of those new hands. One of the more common double downs after a split is to split eights (because it is a split the player should always make) and then have one of those eights get hit with a deuce or a three thereby giving the player, in many situations, a hand upon which the player can double down.

Microgaming does not have this Rule on their best game, their 2nd-6th best games do have this rule. Of course, their best game is a single deck game (with few other favorable rules) though it does allow for deck-composition strategy based play to take place. Playtech also allows doubling after a split on most games.

With respect to the effect of the house edge, we will take a look at both the single deck and the eight deck version of, ‘Awesome Blackjack Game,’ and see what happens with that:

Single Deck: New Player Edge .22133%, difference .15159%

Eight Decks: New House Edge: .25419%, difference .14940%

With what we have learned about splits, it may seem counterintuitive that the difference in the edge would be slightly greater on the single deck game, right? However, it is not and the reason is very simple: Deck composition strategy.

Remember that even though having our ability to split restricted was more detrimental on the eight deck game, having our doubles restricted to 9-11 or 10-11 was more detrimental on the single deck game and a big reason for that was the fact that deck composition strategy is such that there are certain totals of hard eight (and an extra of hard nine) that would result in the player doubling when the player would otherwise not do so. This does not stop being the case with respect to doubling after a split, in fact, doubling after a split will become an even better play if the player ends up with a hard total of eight on one of the split hands against a dealer upcard that calls for a double.

In fact, the only reason that the difference in the edge with single deck doesn’t blow that out of the water with eight decks IS because the player will have the ability to split more frequently in the eight deck game, and as a result, there are more total situations in which the player may split, but the losses incurred by not being able to double after doing so are not as severe.

Once again, the inability to double after splitting does not necessarily make a game what I would consider a bad Blackjack game as there may be other player favorable rules that compensate for this inability. However, if being able to double after splitting is important to you on a standard blackjack game, then you should seek out the best returning game that allows you to do so.

Natural Blackjack

If it is a standard Blackjack game and a player natural does not pay 3:2, then that game can (expletives omitted).


I have spoken to people, good people, who have never played a Blackjack game upon which Surrender was allowed and that makes me sad. Surrender is the ability for a player to say, “No, just no, this hand positively sucks and I want half of my money back now, thank you.

There are some situations in which the casino has too much of an advantage over the player given the way that the cards came out, and the player is better off to just forfeit half of the amount bet because, if the player continues in the hand, the player has an expected value of losing in excess of half of the amount bet.

Due to the way that the deck composition strategy on a single deck game works out mathematically, a player is more likely to surrender in an eight-deck game, and as we will see, the inability to surrender is more detrimental to a player playing an eight deck game than the player playing a single deck game. Once again, we will use our, ‘Awesome Blackjack Game,’ and adjust accordingly.

Single Deck: New Player Edge .35087%, difference .02205%

Eight Decks: New House Edge: .18061, difference .07582%

In the eight deck game, the player will surrender a hard sixteen going up against a dealer nine and a hard fifteen up against a dealer ten, whereas the deck composition (all of the 2’s, 3’s and 4’s remain in the single deck) demands that the player go ahead and take a hit in those situations. The result of that is that a player is more likely to be put in a position to surrender in a game of multiple decks, and therefore, an inability to do so is more detrimental to the player than it would be in a single deck game.

Microgaming allows Surrender in two of their games, which are their second and fifth best games in terms of return. Playtech allows it in one standard Blackjack game, and that game actually happens to be their best game.

As with other Blackjack games, it is the sum of the rules and the effect the rules have on the player that yields a certain house edge, however, Surrender might be a rule that a player would like to demand, and if so, the player should seek out the game with the best return possible that allows the player to surrender.

Number of Decks

I am sure that most of you have gathered this by now, but when fewer decks are used, it allows for a player to play according to deck composition strategy. Essentially, this is similar in concept to card counting and making what are called, ‘Index Plays,’ by which, at a certain count, a player will choose to deviate from basic (or otherwise optimal) strategy because the number of tens remaining in a deck, or some other factor, results in a play that would otherwise not be correct being the correct play. With respect to actual card counting, the most well-known (and valuable) example of an Index Play is that a player will occasionally be correct to take Insurance against a dealer Ace, but you can read more about that elsewhere on this site.

Soft 17’s

The way that a dealer handles soft seventeens is a big factor in the house edge of a particular Blackjack game because standing on soft-17 forces the dealer to keep a not so great hand instead of trying to improve it, which he is very likely to do.

If you need proof of this, simply look at our Blackjack Basic Strategy Engine

You can change any of the rules that you want to, but one thing that will not change is the fact that you always hit or double on soft-17. If hitting or doubling is something that the player should always do, then it clearly stands to reason that the house is going to increase its edge by determining that the dealer must also hit on soft-17 in order to improve his or her hand.

Let us now look at how it affects our, ‘Awesome Blackjack Game,’ for both single deck and eight decks:

Single Deck: New Player Edge .19733%, difference .17559%

Eight Deck: New House Edge .30602%, difference .20123%

There is actually not much of a difference in the way that the house edge is affected, however, because most soft-17’s will be A-6, it stands to reason that there are fewer, ‘Good cards,’ for the dealer from a deck composition standpoint because another Ace would give the dealer a Hard-18 and there are fewer Aces available relative to the remaining cards in the single deck game. There are probably other reasons besides that, so if you think of any of them, please mention it in the comments!

Part 1 Conclusion:

With that, we have looked at the Rule Variants of what is otherwise a standard Blackjack game, and what is fascinating is the way that the house edge can fluctuate dramatically given each individual rule change that, by themselves, may seem unimportant. Our single-deck, ‘Awesome Blackjack Game,’ has a player advantage of .37292%, but if we switch every other rule to be less advantageous to the player and make the game eight decks (except I am not switching Blackjacks to 6:5 or I will vomit all over my office) we end up with a house edge of 1.1089%!!!

Okay, just for the Hell of it I am going to make all of the rules optimal for the player, except I am going to make Blackjack pay 6:5, and…

The House Edge is 1.02185% on a single deck game, on eight decks, it’s 1.46278%, remember, that’s with otherwise great rules.

6:5 Blackjack is a disgusting abomination that I will never speak allowed for fear of condemning myself to eternal fire and brimstone for even having the audacity to allow such dreadful and hateful words to escape my lips. DO NOT PLAY 6:5 BLACKJACK, NOT ONLINE, NOT LIVE, NOT ANYWHERE!!! Friends don’t let friends play 6:5 Blackjack!!! Just say no!

I think I feel better now, so let’s look at some fun little Blackjack variants!