Ideally, blackjack would be played under a single set of rules in all locations, so that once a player had learned the game, he could approach any table in any casino with confidence. Unfortunately, that's not the case.
Casinos vary the rules in order to adjust the profitability of the game, invariably in their own interest: some rules are in effect to increase their profit on a given table, others to decrease it so that players will not be discouraged to play at their tables at all. The net effect of these decisions is described in greater detail in the "odds" section.
For now, here are some of the variations you may encounter.
The only rule that pertains to the amount a player may wager is the table minimum/maximum. Typically, table minimums are set at $5, $10, $25, $50, and $100 increments, with the maximum being 1,000 times the minimum amount.
A minimum amount is put in effect to ensure a given profitability at a table (compelling players to risk at least a certain amount, or make room for those who will). The maximum is enforced to defeat a very effective wagering system called "Martingale" (discussed in the intermediate strategy section of this site).
Table limits are generally set according to supply and demand. During high-volume periods (such as weekends, especially holiday weekends), table limits are increased because there are enough high-limit gamblers to fill them. If the traffic is low, especially if there are a lot of potential players observing games but not joining in, the limits may be lowered (or lower-limit tables opened) to encourage low-limit gamblers to play.
Decks Per Shoe and Cards Per Deck
Another common variation is the number of decks put into play. Since the proportion of the cards are the same regardless of the number of decks, this does not affect the rules of the game, per se, but it does have a sleight effect on the chances of winning. Simply stated, the more decks, the better the house's edge.
Also, most casinos do not allow the dealer to play every card in the decka few decks may be cut out of a shoe, or only a certain number of hands may be played from a deck, before the cards are reshuffled. This practice was established to decrease or eliminate the advantage gained by counting cards (a technique described in the "advanced strategy" section). Casinos have been known to increase the frequency of the shuffle if one or more players seem to be winning consistently.
In some cases, constant shuffling machines (CSMs) are used to shuffle the cards between every round. This does not seem to be a widespread practice in casinos in the United States, though there are rumors CSMs are being used more frequently overseas. It's also worth mentioning that blackjack games in most internet-based casinos are programmed to randomize in a way that has the same net effect.
In some cases, the deck itself is altered by removing certain cards. Fortunately, casinos generally have the decency to run such games under a different name, such as "Spanish 21" - a game in which the deck is stripped of tens and the player is offered a handful of additional playing options in exchange for the severe disadvantage created by altering the deck in this manner.
Other rules are in place to limit the player's optionsor more aptly, to eliminate some of the more profitable options. If you've read the "blackjack basics" page, you've already learned a few of these: players cannot make more than four hands by splitting; players receive only one card on split aces; players can only surrender at the beginning of the hand. These restrictions may be rescinded, or others imposed.
A player may be allowed to ...
- split more than three times, or only once
- take more than one card on split aces
- take only one card on a split tens (or any split hand)
- surrender late (after taking hits), early (only after the first two cards are dealt) or not at all
- double only on certain totals (typically ten or eleven)
- double at any time (even after taking hits)
Altering Odds and Payoffs
Casinos may offer 2:1 odds on a player's blackjack (or certain blackjacksfor example, if ten and ace are of the same suit), or continue to pay 3:2 on player's blackjack when the dealer has one. This is very rare, because the bonus to the skilled player is tremendous.
On the other side of the coin, there's a "no hole card" variation where the dealer does not take a second card until all hands have been playedand if the dealer draws a blackjack, the house also claims increased wagers from players who have split hands or doubled their wagers.
Altering Dealer Play
The most common variation in the dealer's play is determining the point at which the dealer must stand. In most games, the dealer is compelled to draw to seventeen. The only common variation to this convention is that a dealer may hit a soft seventeen.
Another alteration to the dealer's practice is exposing the hole card to players. This variation, billed as "double exposure" blackjack, provides a tremendous advantage to the players, so it is not uncommon for the house to regain its edge by other means. At the very least, the "surrender" option is rescinded, and it is not uncommon fordoubling and splitting of hands to be restricted or forbidden. As well, the payoff on blackjack may be reduced to even money and the dealer usually wins ties.