Blackjack Variants

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. There are blackjack variants which affect your winning odds greatly.

Casinos vary the rules to adjust the profitability of the game, invariably in their 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.

The most common way for a casino to manage its desire to turn a high profit against the player’s demand to have a fair chance at winning is to adjust the rules of the game, increasing or decreasing its own advantage. Here are the effects that various rules have on the outcome of the game:

Wagering Limits

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 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 useful wagering system called “Martingale” (discussed in the basic strategy section of this site). Setting a minimum limit to wagering amounts does not affect the outcome of hands played at the table, but it does affect the amount of profit the casino will take from the players. Simply by raising the table minimum from $5 to $10 will double the profit that will be turned.

Wagering Limits

The table maximum likewise has no effect on the outcome of hands, but neither does it improve the house’s profits. Table maximums were implemented in order to defeat the Martingale system, a highly effective strategy (discussed in the intermediate strategies 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.

But by far, the most effective wagering limitation casinos employ is the option to refuse to allow a player to wager at all—in effect, to throw him out of the game, or even the casino. Regardless of the strategy a player utilizes, he can expect to be asked to leave the table (or forcibly ejected) if he seems to be winning consistently. Though it’s certainly not something the casino industry wants to be known, the best strategy for a casino to make profit is to allow only losing players to participate, and show winners to the door.

Decks Per Shoe

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 slight 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 deck—a 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, continuous 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 rumours CSMs are being used more frequently overseas. It’s also worth mentioning that blackjack games in most internet-based casinos are programmed to randomise 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.

Once the first card has been dealt, it is no longer available, so the odds of drawing a card of the same value (making a pair) are less. To be precise, the odds are 3 in 51 (about 1.8% less) in a single-deck game, 7 in 103 in a double-deck game (1.2% less), and so on, with the odds diminishing as more decks are added. As more cards are drawn, the odds are further skewed.

Though pairs are “exciting” to the player who expects to win both hands, this is not the most likely outcome. In most cases, pair-splitting is done to salvage a bad hand, in hopes of winning only one of the split hands to break even. As a result, the more decks, the more pairs, and the more risk a player must assume in unfavorable situations, just to break even.

Pairs are also likely to show up on the dealer’s side. Although the dealer cannot split pairs to salvage the round, neither does the house lose twice as much when both split hands lose—so the effects of an increased incidence of pairs are not the same on both sides of the table. Though the house may lose a greater number of hands that begin with paired cards, it will lose less money when these losses occur.

The effects of increased pairs to the player’s odds are:

Two deck (vs. single deck) -0.35
Four deck (vs. single deck) -0.51
Six deck (vs. single deck) -0.60

Betting Limits

Other rules are in place to limit the player’s options—or 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 …

  1. split more than three times, or only once
  2. take more than one card on split aces
  3. take only one card on split tens (or any split hand)
  4. surrender late (after taking hits), early (only after the first two cards are dealt) or not at all
  5. double only on certain totals (typically ten or eleven)
  6. double at any time (even after taking hits)

Limiting Options: Surrender

It is in the player’s surrender in situations in which his chances of winning are less than 50%. Typically, the player is allowed to surrender on the initial hand (“early surrender”) and, in rare cases, a player may surrender late. The option to surrender may be restricted according to the value of the dealer’s upcard. The effect of surrender variations on the core odds are:


Early Surrender vs. anything +0.62%
Early surrender vs. ace (only) +0.39%
Early surrender vs. ten (only) +0.24%
Late Surrender vs. anything +0.07%
Late surrender vs. ace (only) +0.00%
Late surrender vs. ten (only) +0.07%

Limiting Options: Doubling

A player’s ability to double has a dramatic affect on a player’s potential winnings—but also has a dramatic effect on his losses. In general, the ability to double on any initial hand (including split hands) increases the player’s advantage by 1.83%. Naturally, many casinos seek to recapture this margin by limiting the player’s opportunities to take advantage of doubling.

Double 9-11 only -0.09%
Double 10-11 only -0.18%
No doubling soft hands -0.14
No doubling after split -0.13

In rare cases, the house may allow a player to “double late”—adding the option to double after the hand has already been hit. When this option is available, it increases the player’s advantage by only 0.20% (as it’s rare that a third or fourth card will yield a hand that should logically be doubled).

Limiting Options: Splitting

In the typical game, a player may split up to four times. In a single-deck game, this is the absolute limit, as there are only four cards of a value in the deck. In multiple-deck games, the likelihood of being able to split a fifth, sixth, etc. time is so remote that the on the odds is negligible. If a player may split only once, however, the effect on his advantage is -0.10%

Also, it is typical for the player to receive only one card on split aces, and not to be able to split them further. If allowed to take hits split aces, the player gains an advantage of 0.14%—and if allowed to re-split them if another ace is drawn, and additional 0.03%.

Splitting cards

Altering Odds and Payoffs

Casinos may offer 2:1 odds on a player’s blackjack (or certain blackjacks—for 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 played—and 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 for doubling 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.

Dealer Wins Pushes

An exceptionally greedy house will change the rules of the game—so that a player who does not beat the dealer’s hand will lose his wager, even if the hands are of equal value. This has a devastating effect on a player’s odds (decrease by 9.4%). To increase the take without scaring off all the players, the house may declare that the dealer wins only certain ties:

Dealer wins ties at 17 -1.87%
Dealer wins ties at 18 -1.71%
Dealer wins ties at 19 -1.72%
Dealer wins ties at 20 -3.08%
Dealer wins ties at 20 -1.02%

The net effect of these variations on the chances of winning is discussed separately, though this information might make more sense after reviewing the core chances of winning.

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