In the game of blackjack, subtle variations in the rules can improve the player’s chances of winning, or they can decrease the player’s chances of winning. The measuring stick for this improvement (or lack of improvement) is measured in terms of the house edge.

In simple terms, the house edge is the percentage of each bet that the casino mathematically expects to win over the long run. For example, when someone plays a game with a house edge of 1%, the house expects to keep $1 for every $100 the player puts into action over time. So if a player is betting $100 per bet on average, and she’s playing 60 hands per hour, then she’s wagering $6000 per hour. If the house has a 1% edge, the casino expects to make $60 per hour from that player.

This amount varies because of standard deviation. In the short term, anything can (and often will) happen. Standard deviation and the short term are the mathematical principles that send some players home as winners. The house edge and the long run are the mathematical principles that make the casinos profitable.

The purpose of this page is to look at some of the rules variations in blackjack that benefit the player, not the casino. That’s why we call them “positive variations”. For most blackjack players, this reduces the amount of money they lose over time, but for card counters and other advantage players, these positive variations can actually affect how profitable the player expects to be over time.

The first rules variation that affects the edge in blackjack is how many decks are in use. The standard in most casinos now is 8 decks, so the fewer decks you’re playing against, the better your odds are. Playing against 6 decks instead of 8 provides you with an extra 0.02%. Playing against 5 decks provides you with 0.03%. Four decks doubles that to 0.06%. A double deck game improves your odds by 0.18%, but the best game, in terms of number of decks, is the single deck game, which is 0.48% better than the 8 deck game.

0.48% doesn’t sound like much, but it’s almost 50 cents per hour when playing for $100 a bet. In some games, this is the difference between profitability and losing when counting cards. The appropriate way to think about these differences is over the long run, and 0.48% is a big deal over the long term.

90% or more of the blackjack games you’ll find will offer 3 to 2 payouts on a natural. A natural (or a blackjack) is a two card hand that totals 21, and the casino pays out 3 to 2 on such a win. This is where most of the edge comes from when counting, because the counter is raising her bets when the deck is rich in tens and aces. That higher payout improves the player’s odds dramatically.

In recent years, casinos have started offering blackjack games with seemingly-attractive rules variations that include a lower payout on naturals. These are often called 6:5 games, because instead of paying 3 to 2 on a blackjack, they pay 6 to 5.

This seems like a small difference, but it’s a play on the naivete of the average casino-goer. Everyone knows that single deck blackjack is better than multi-deck blackjack, but the difference between 6:5 and 3:2 blackjack makes up for that 0.48% difference and then some. The difference here is 1.39%, so the casino has a net gain of over 1% when offering a single deck game with a 6 to 5 payout.

Blackjack that pays even odds on a natural is even worse. The casino gains a whopping 2.27% from this rules variation. Ugh!

The best advice you’ll ever see about positive rules variations in blackjack is to stick with the games offering 3 to 2 payouts on a natural.

A blackjack game in which a player can double down on any 2 cards offers a 0.23% improvement to the player. The reasons for this should be obvious—sometimes when the dealer has a stiff hand, the player might double down with something other than a 10 or an 11 in order to get more money into action in the hopes that the dealer will bust.

Also, if a player is counting cards, doubling down will sometimes be a deviation from basic strategy that makes sense in certain situations but not others. This makes this rules variation even more important. Besides insisting on single deck blackjack with 3 to 2 payouts, this is the most important rules variation to look for.

A five card Charlie is a hand with 5 cards that doesn’t bust. (You can probably figure out what a 6 card Charlie is based on that, right?) In some games, a “Charlie” is an automatic win. If a casino has a five card Charlie rule in effect, then the player gains 1.46%, making this a huge advantage for the player. The six card Charlie is also advantageous, gaining the player 0.16%.

These rules variations are a little rarer than some of the other variations discussed on this page.

One of the first tenets of blackjack basic strategy that everyone learns early in their casino gambling career is that you should always split aces. That’s because there are more 10s in the deck than any other card, and if you split your aces, you get two opportunities to draw to a natural, which pays out at 3 to 2.

Some casinos allow you to only receive only one additional card when splitting aces, but if you’re allowed to draw additional cards beyond that, you gain 0.19%. If you’re allowed to split again after you get dealt an additional ace after splitting, you gain another 0.08%.

It doesn’t matter how favorable the rules are if you don’t follow basic strategy. That’s the mathematically correct play for every situation in blackjack, and you should never deviate from it based on hunches. Blackjack is a game of math, and there is no such thing as luck—just standard deviation.

If you ignore basic strategy, you’re giving up between 2-4% to the casino. None of the positive rules variations matter if you’re ignoring basic strategy and just winging it.