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Variation In Blackjack Rules
How They Affect The House Edge

By Henry Tamburin

As you browse the blackjack tables in your favorite casino you notice they offer a double-deck game and also a six-deck game. The rules for each game, however, are different and happen to be:


Double-deck game:  dealer hits soft 17, you can double down on any first two cards, players can double down after pair splitting, you can resplit up to three hands, you can’t resplit aces, and surrender is not allowed. (The abbreviations of the rules for this game are: DD, H17, DOA, DAS, RSP3.)


Six-deck game: dealer stands on soft 17, you can double down on any first two cards, players can double down after pair splitting, you can resplit aces (and non-aces) up to four hands, and late surrender is offered (6D, S17, DOA, DAS, RSA4, RSP4, LS).


Assuming the table minimums are the same for both games, and you are playing basic strategy, without card counting, which one would you play?


Before I tell you which game is better, let me pose another question to you: How many variations in rules are there in the game of blackjack? 5? 10? 20? Guess again ... according to there are over 30 of them (and this doesn’t include the obscure rules and variations of the game). And guess what? Each rule impacts the house edge (some more than others) and thus your chance of winning. Therefore, the goal of this article is to give you some tips to help guide you in selecting the best blackjack game.


There are two important variables that affect the house edge: the number of decks of cards being used, and the playing rules.


Number of decks of cards
The casino’s edge (in percent) against a basic strategy player increases as the number of decks of cards used increases. The following table* shows this relationship.


1 Deck

2 Decks

4 Decks

6 Decks

8 Decks







*The percentages were taken from the book Blackjack Attack: Playing the Pros’ Way. It assumes a benchmark game with these rules: dealer stands on soft 17, you can double down on any first two cards, double after pair splitting is not allowed, you can split aces only once and non-aces up to four hands, and surrender is not allowed.


Notice that the casino’s edge is negative 0.033 percent in the single-deck game (meaning a basic strategy player would actually have the edge against the casino in this game), and the casino’s edge gets progressively more positive as the number of decks increases (i.e., the edge shifts to the casino when two or more decks are used, and the casino’s edge progressively increases as the number of decks of cards increases). Notice, also, that the biggest incremental increase in casino edge occurs when you go from a single- to a two-deck game, and then the increase becomes less onerous as you add more decks of cards (which is why casinos rarely use more than eight decks).


What these data mean for players is this: if all else is equal, a single-deck game is a better game than a two-deck game, which is likewise better than a four-deck game, and so on. However, “all else is equal” is often not the case in the casino, which is why we need to also look at the effect the playing rules (and payoffs) have on the house edge.


As I mentioned earlier, you could encounter many different rules when you play blackjack. Sometimes playing rules are mandated by local regulations, but more often than not they are selected by the casinos themselves. Every rule impacts the casino’s edge, and it’s important that you know which ones are more “player friendly” and which ones favor the casino.


Player-Friendly Rules
Dealer stands on soft 17
Doubling down on any first two cards
Doubling down after pair splitting
Resplitting pairs
Resplitting aces
Blackjack pays 2-1


Casino-Friendly Rules
Dealer hits soft 17
Multiple decks of cards
Blackjack pays 6-5 or, worse, even money
Doubling only on 9, 10, or 11 (or just 10 and 11)
Doubling down after pair splitting not allowed
No resplitting of aces
No surrender
No hole card (and players lose original and secondary bets to a dealer blackjack)


Notice that the payoffs for a blackjack can influence the casino’s edge one way or the other. For example, compared to the traditional 3-2 payoff, a game that pays blackjacks at only 6-5 (or, worse, even money) is very much a casino-friendly rule (the house edge increases 1.39 percent in a single-deck game with a 6-5 payoff and  2.3 percent for an even money payoff). On the other hand, if you get wind of a promotion where a casino is paying a generous 2-1 for a blackjack, run (don’t walk) to play this game because a 2-1 payoff will decrease the casino’s edge by 2.3 percent often resulting in a game that gives players a healthy advantage over the casino.


In an ideal world it’s best to play a blackjack game that has only a mix of player-friendly rules. But it’s rare that you will find this game.  For example, you might find a double-deck game (good) but the dealer hits soft 17 (bad), or a six-deck game (bad) where the dealer stands on soft 17 (good) and surrender is offered (good). So how can you determine which game is best when you are often confronted with a cornucopia of different blackjack games in the casino? Easy. Go to the Internet and use any number of blackjack calculators that will allow you to quickly obtain a rough-and-dirty estimate of the house edge of any game based on the number of decks of cards and the playing rules.


Here’s an example.  One of the easiest calculators to use is at (blackjack page). They have a drop-down menu where you just click on the different rules and the computer will automatically calculate the house edge. For example, the calculator estimates the house edge for the two games that I mentioned at the beginning of this article as follows:


DD, H17, DOA, DAS, RSP3: 0.46% casino edge.
6D, S17, DOA, DAS, RSA4, RSP4, LS: 0.28% casino edge.


For a recreational player (non card counting), the six-deck game with the lower casino edge would be a better choice than the double-deck game.


With tools like the house-edge calculator, it’s easy to estimate the casino edge of any blackjack game, or to compare one game with another to determine which one has the lowest edge. And what if you run across a game with an odd rule (for example, earlier surrender but only against an ace)?  I’d suggest in this case that you consult the extensive list of rule variations on pages 492 and 493 (Table C1) of Blackjack Attack.