Blackjack (formerly Black Jack and Vingt-Un) is the most widely played casino banking game in the world.:342 The game is played with decks of 52 cards and is an American descendant of a global family of banking games known as Twenty-One. This family of card games also includes the British game of Pontoon and the European game, Vingt-et-Un.
Blackjack players do not compete against each other. The game is a comparing card game where each player competes against the dealer.
Blackjack's immediate precursor was the English version of twenty-one called Vingt-Un, a game of unknown (but probably Spanish) provenance. The first written reference is found in a book by the Spanish author Miguel de Cervantes. Cervantes was a gambler, and the protagonists of his "Rinconete y Cortadillo", from Novelas Ejemplares, are card cheats in Seville. They are proficient at cheating at veintiuna (Spanish for "twenty-one") and state that the object of the game is to reach 21 points without going over and that the ace values 1 or 11. The game is played with the Spanish baraja deck.
"Rinconete y Cortadillo" was written between 1601 and 1602, implying that ventiuna was played in Castile since the beginning of the 17th century or earlier. Later references to this game are found in France and Spain.
The first record of the game in France occurs in 1768 and in Britain during the 1770s and 1780s, but the first rules appear in Britain in 1800 under the name of Vingt-Un. Twenty-One, still known then as Vingt-Un, appeared in the United States in the early 1800s. The first American rules were an 1825 reprint of the 1800 English rules. English Vingt-Un later developed into an American variant in its own right which was renamed blackjack around 1899.
According to popular myth, when Vingt-Un ("Twenty-One") was introduced into the United States (in the early 1800s, during the First World War, or in the 1930s, depending on the source), gambling houses offered bonus payouts to stimulate players' interest. One such bonus was a ten-to-one payout if the player's hand consisted of the ace of spades and a black jack (either the jack of clubs or the jack of spades). This hand was called a "blackjack", and the name stuck even after the ten-to-one bonus was withdrawn.
French card historian, Thierry Depaulis debunks this story, showing that prospectors during the Klondike Gold Rush (1896–99) gave the name blackjack to the game of American Vingt-Un, the bonus being the usual ace and any 10-point card. Since 'blackjack' also refers to the mineral zincblende, which was often associated with gold or silver deposits, he suggests that the mineral name was transferred by prospectors to the top bonus hand. He was unable to find any historical evidence for a special bonus for having the combination of an ace with a black jack.
In September 1956, Roger Baldwin, Wilbert Cantey, Herbert Maisel, and James McDermott published a paper titled The Optimum Strategy in Blackjack in the Journal of the American Statistical Association., the first mathematically sound optimal blackjack strategy. This paper became the foundation of future efforts to beat blackjack. Ed Thorp used Baldwin's hand calculations to verify the basic strategy and later published (in 1963) Beat the Dealer.
At a blackjack table, the dealer faces five to seven playing positions from behind a semicircular table. Between one and eight standard 52-card decks are shuffled together. To start each round, players place bets in the "betting box" at each position. In jurisdictions allowing back betting, up to three players can be at each position. The player whose bet is at the front of the betting box controls the position, and the dealer consults the controlling player for playing decisions; the other bettors "play behind". A player can usually control or bet in as many boxes as desired at a single table, but an individual cannot play on more than one table at a time or place multiple bets within a single box. In many U.S. casinos, players are limited to playing one to three positions at a table.
The dealer deals from their left ("first base") to their far right ("third base"). Each box gets an initial hand of two cards visible to the people playing on it. The dealer's hand gets its first card face up, and, in "hole card" games, immediately gets a second card face down (the hole card), which the dealer peeks at but only reveals when it makes the dealer's hand a blackjack. Hole card games are sometimes played on tables with a small mirror or electronic sensor used to peek securely at the hole card. In European casinos, "no hole card" games are prevalent; the dealer's second card is not drawn until the players have played their hands.
Dealers deal the cards from one or two handheld decks, from a dealer's shoe, or from a shuffling machine. Single cards are dealt to each wagered-on position clockwise from the dealer's left, followed by a single card to the dealer, followed by an additional card to each of the positions in play. The players' initial cards may be dealt face up or face down (more common in single-deck games).
The object of the game is to win money by creating card totals higher than those of the dealer's hand but not exceeding 21, or by stopping at a total in the hope that dealer will bust. On their turn, players choose to "hit" (take a card), "stand" (end their turn and stop without taking a card), "double" (double their wager, take a single card, and finish), "split" (if the two cards have the same value, separate them to make two hands), or "surrender" (give up a half-bet and retire from the game).
Number cards count as their number, the jack, queen, and king ("face cards" or "pictures") count as 10, and aces count as either 1 or 11 according to the player's choice. If the total exceeds 21 points, it busts, and all bets on it immediately lose.
After the boxes have finished playing, the dealer's hand is resolved by drawing cards until the hand achieves a total of 17 or higher (a dealer total of 17 including an ace valued as 11, also known as a "soft 17", must be drawn to in some games and must stand in others). The dealer never doubles, splits, or surrenders. If the dealer busts, all remaining player hands win. If the dealer does not bust, each remaining bet wins if its hand is higher than the dealer's and loses if it is lower.
A player total of 21 on the first two cards is a "natural" or "blackjack," and the player wins immediately unless dealer also has one, in which case the hand ties. In the case of a tie ("push" or "standoff"), bets are returned without adjustment. But a blackjack beats any hand that is not a blackjack, even one with a value of 21.
Wins are paid out at even money, except for player blackjacks, which are traditionally paid out at 3 to 2 odds. Many casinos today pay blackjacks at less than 3:2. This is common in single-deck blackjack games.
Blackjack games usually offer a side bet called insurance, which may be placed when the dealer's face up card is an ace. Additional side bets, such as "Dealer Match" which pays when the player's cards match the dealer's up card, are also sometimes available.
After the initial two cards, the player has up to five options: "hit", "stand", "double down", "split", or "surrender". Each option has a corresponding hand signal.
Hand signals help the "eye in the sky" make a video recording of the table, which resolves disputes and identifies dealer mistakes. It is also used to protect the casino against dealers who steal chips or players who cheat. Recordings can also identify advantage players. When a player's hand signal disagrees with their words, the hand signal takes precedence.
A hand can "hit" as many times as desired until the total is 21 or more. Players must stand on a total of 21. After a bust or a stand, play proceeds to the next hand clockwise around the table. After the last hand is played, the dealer reveals the hole card and stands or draws according to the game's rules. When the outcome of the dealer's hand is established, any hands with bets remaining on the table are resolved (usually in counterclockwise order); bets on losing hands are forfeited, the bet on a push is left on the table, and winners are paid out.
If the dealer shows an ace, an "insurance" bet is allowed. Insurance is a side bet that the dealer has a blackjack. The dealer asks for insurance bets before the first player plays. Insurance bets of half the player's current bet are placed on the "insurance bar" above player's cards. If the dealer has a blackjack, insurance pays 2 to 1. In most casinos, the dealer looks at the down card and pays off or takes the insurance bet immediately. In other casinos, the payoff waits until the end of the play.
In face-down games, if a player has more than one hand, they are allowed to look at all their hands before deciding. This is the only condition where a player can look at multiple hands.
Insurance bets lose money in the long run. The dealer has a blackjack less than one-third of the time. Players can also take insurance when a 10-valued card shows, but the dealer has an ace in the hole less than one-tenth of the time.
The insurance bet is susceptible to advantage play. It is advantageous to make an insurance bet whenever the hole card has more than a one in three chance of being a ten. Card counting techniques can identify such situations.
Note: where changes in the house edge due to changes in the rules are stated in percentage terms, the difference is usually stated here in percentage points, not percentage. For example, if an edge of 10% is reduced to 9%, it is reduced by one percentage point, not reduced by ten percent.
Blackjack rules are generally set by regulations which establish permissible rule variations at the casino's discretion. These variations are posted on or near the table. Players can ask the dealer about unclear rules. Over 100 rules variations have been documented.
Blackjack comes with a "house edge"; the casino's statistical advantage is built into the game. Most of the house's edge comes from the fact that the player loses when both the player and dealer bust. Blackjack players using basic strategy lose less than an average of 1% of their action over the long run, giving blackjack one of the lowest edges in the casino. The house edge for games where blackjack pays 6 to 5 instead of 3 to 2 increases by about 1.4%, though. Player deviations from basic strategy also increase the house edge.
Each game has a rule about whether the dealer must hit or stand on soft 17, which is generally printed on the table surface. The variation where the dealer must hit soft 17 is abbreviated "H17" in blackjack literature, with "S17" used for the stand-on-soft-17 variation. Substituting an "H17" rule with an "S17" rule in a game benefits the player, decreasing the house edge by about 0.2%.
All things being equal, using fewer decks decreases the house edge. This mainly reflects an increased likelihood of player blackjack, since if the players draws a ten on their first card, the subsequent probability of drawing an ace is higher with fewer decks. It also reflects a decreased likelihood of blackjack-blackjack push in a game with fewer decks.
Casinos generally compensate by tightening other rules in games with fewer decks, in order to preserve the house edge or discourage play altogether. When offering single deck blackjack games, casinos are more likely to disallow doubling on soft hands or after splitting, to restrict resplitting, require higher minimum bets, and to pay the player less than 3:2 for a winning blackjack.
The following table illustrates the mathematical effect on the house edge of the number of decks, by considering games with various deck counts under the following ruleset: double after split allowed, resplit to four hands allowed, no hitting split aces, no surrender, double on any two cards, original bets only lost on dealer blackjack, dealer hits soft 17, and cut-card used. The increase in house edge per unit increase in the number of decks is most dramatic when comparing the single deck game to the two-deck game, and becomes progressively smaller as more decks are added.
Surrender, for those games that allow it, is usually not permitted against a dealer blackjack; if the dealer's first card is an ace or ten, the hole card is checked to make sure there is no blackjack before surrender is offered. This rule protocol is consequently known as "late" surrender. The alternative, "early" surrender, gives player the option to surrender before the dealer checks for blackjack, or in a no hole card game. Early surrender is much more favorable to the player than late surrender.
For late surrender, however, while it is tempting to opt for surrender on any hand which will probably lose, the correct strategy is to only surrender on the very worst hands, because having even a one in four chance of winning the full bet is better than losing half the bet and pushing the other half, as entailed by surrendering.
If the cards of a post-split hand have the same value, most games allow the player to split again, or "resplit". The player places a further wager and the dealer separates the new pair dealing a further card to each as before. Some games allow unlimited resplitting, while others may limit it to a certain number of hands, such as four hands (for example, "resplit to 4").
After splitting aces, the common rule is that only one card will be dealt to each ace; the player cannot split, double, or take another hit on either hand. Rule variants include allowing resplitting aces or allowing the player to hit split aces. Games allowing aces to be resplit are not uncommon, but those allowing the player to hit split aces are extremely rare. Allowing the player to hit hands resulting from split aces reduces the house edge by about 0.13%; allowing resplitting of aces reduces house edge by about 0.03%. Note that a ten-value card dealt on a split ace (or vice versa) will not be counted as a blackjack, but as a soft 21.
After a split, most games allow doubling down on the new two-card hands. Disallowing doubling after a split increases the house edge by about 0.12%.
Under the "Reno rule", double down is only permitted on hard totals of 9, 10, or 11 (under a similar European rule, only 10 or 11). Basic strategy would otherwise call for some doubling down with hard 9 and soft 13–18, and advanced players can identify situations where doubling on soft 19–20 and hard 8, 7 and even 6 is advantageous. The Reno rule prevents the player from taking advantage of double down in these situations and thereby increases the player's expected loss. The Reno rule increases the house edge by around 1 in 1,000, and its European version by around 1 in 500.
In most non-U.S. casinos, a "no hole card" game is played, meaning that the dealer does not draw nor consult their second card until after all players have finished making decisions. With no hole card, it is almost never correct basic strategy to double or split against a dealer ten or ace, since a dealer blackjack will result in the loss of the split and double bets; the only exception is with a pair of aces against a dealer 10, where it is still correct to split. In all other cases, a stand, hit or surrender is called for. For instance, holding 11 against a dealer 10, the correct strategy is to double in a hole card game (where the player knows the dealer's second card is not an ace), but to hit in a no hole card game. The no hole card rule adds approximately 0.11% to the house edge.
The "original bets only" rule variation appearing in certain no hole card games states that if the player's hand loses to a dealer blackjack, only the mandatory initial bet ("original") is forfeited, and all optional bets, meaning doubles and splits, are pushed. "Original bets only" is also known by the acronym OBO; it has the same effect on basic strategy and house edge as reverting to a hole card game.
In many casinos, a blackjack pays only 6:5 or even 1:1 instead of the usual 3:2. This is most common at tables with lower table minimums. Although this payoff was originally limited to single-deck games, it has spread to double-deck and shoe games. Among common rule variations in the U.S., these altered payouts for blackjack are the most damaging to the player, causing the greatest increase in house edge. Since blackjack occurs in approximately 4.8% of hands, the 1:1 game increases the house edge by 2.3%, while the 6:5 game adds 1.4% to the house edge. Video blackjack machines generally pay 1:1 payout for a blackjack.
The rule that bets on tied hands are lost rather than pushed is catastrophic to the player. Though rarely used in standard blackjack, it is sometimes seen in "blackjack-like" games such as in some charity casinos.
Each blackjack game has a basic strategy, the optimal method of playing any hand. When using basic strategy, the long-term house advantage (the expected loss of the player) is minimized.
An example of a basic strategy is shown in the table below, which applies to a game with the following specifications:
Most basic strategy decisions are the same for all blackjack games. Rule variations call for changes in only a few situations. For example, to use the table above on a game with the stand on soft 17 rule (which favors the player, and is typically found only at higher-limit tables today) only 6 cells would need to be changed: hit on 11 vs. A, hit on 15 vs. A, stand on 17 vs. A, stand on A,7 vs. 2, stand on A,8 vs. 6, and split on 8,8 vs. A. Regardless of the specific rule variations, taking insurance or "even money" is never the correct play under basic strategy.
Estimates of the house edge for blackjack games quoted by casinos and gaming regulators are based on the assumption that the players follow basic strategy.
Most blackjack games have a house edge of between 0.5% and 1%, placing blackjack among the cheapest casino table games for the player. Casino promotions such as complimentary match play vouchers or 2:1 blackjack payouts allow the player to acquire an advantage without deviating from basic strategy.
Basic strategy is based upon a player's point total and the dealer's visible card. Players can sometimes improve on this decision by considering the composition of their hand, not just the point total. For example, players should ordinarily stand when holding 12 against a dealer 4. But in a single deck game, players should hit if their 12 consists of a 10 and a 2. The presence of a 10 in the player's hand has two consequences:
Even when basic and composition-dependent strategies lead to different actions, the difference in expected reward is small, and it becomes smaller with more decks. Using a composition-dependent strategy rather than basic strategy in a single deck game reduces the house edge by 4 in 10,000, which falls to 3 in 100,000 for a six-deck game.
Blackjack has been a high-profile target for advantage players since the 1960s. Advantage play is the attempt to win more using skills such as memory, computation, and observation. These techniques, while legal, can give a player a matheamtical edge in the game, making advantage players unwanted customers for casinos. Advantage play can lead to ejection or blacklisting. Some advantage play techniques in blackjack include:
During the course of a blackjack shoe, the dealer exposes the dealt cards. Players can infer from their accounting of the exposed cards which cards remain. These inferences can be used in the following ways:
A card counting system assigns a point score to each rank of card (e.g., 1 point for 2–6, 0 points for 7–9 and −1 point for 10–A). When a card is exposed, a counter adds the score of that card to a running total, the 'count'. A card counter uses this count to make betting and playing decisions. The count starts at 0 for a freshly shuffled deck for "balanced" counting systems. Unbalanced counts are often started at a value which depends on the number of decks used in the game.
Card counting works best when few cards remain. This makes single-deck games better for counters. As a result, casinos are more likely to insist that players do not reveal their cards to one another in single-deck games. In games with more decks, casinos limit penetration by ending the shoe and reshuffling when one or more decks remain undealt. Casinos also sometimes use a shuffling machine to reintroduce the cards every time a deck has been played.
Card counting is legal unless the counter is using an external device,:6–7 but a casino might inform counters that they are no longer welcome to play blackjack. Sometimes a casino might ban a card counter from the property.
The use of external devices to help counting cards is illegal throughout the United States.
Another advantage play technique, mainly applicable in multi-deck games, involves tracking groups of cards (also known as slugs, clumps, or packs) through the shuffle and then playing and betting according to when those cards come into play from a new shoe. Shuffle tracking requires excellent eyesight and powers of visual estimation but is harder to detect; shuffle trackers' actions are largely unrelated to the composition of the cards in the shoe.
Arnold Snyder's articles in Blackjack Forum magazine brought shuffle tracking to the general public. His book, The Shuffle Tracker's Cookbook, mathematically analyzed the player edge available from shuffle tracking based on the actual size of the tracked slug. Jerry L. Patterson also developed and published a shuffle-tracking method for tracking favorable clumps of cards and cutting them into play and tracking unfavorable clumps of cards and cutting them out of play.
The player can also gain an advantage by identifying cards from distinctive wear markings on their backs, or by hole carding (observing during the dealing process the front of a card dealt face down). These methods are generally legal although their status in particular jurisdictions may vary.
Many blackjack tables offer side bets on various outcomes including:
The side wager is typically placed in a designated area next to the box for the main wager. A player wishing to wager on a side bet is usually required to place a wager on blackjack. Some games require that the blackjack wager should equal or exceed any side bet wager. A non-controlling player of a blackjack hand is usually permitted to place a side bet regardless of whether the controlling player does so.
The house edge for side bets is generally higher than for the blackjack game itself. Nonetheless, side bets can be susceptible to card counting. A side count designed specifically for a particular side bet, can improve the player edge. Only a few side bets, like "Lucky Ladies", offer a sufficient win rate to justify the effort of advantage play.
In team play it is common for team members to be dedicated toward counting only a sidebet using a specialized count.
Blackjack can be played in tournament form. Players start with an equal numbers of chips; the goal is to finish among the top chip-holders. Depending on the number of competitors, tournaments may be held over several rounds, with one or two players qualifying from each table after a set number of deals to meet the qualifiers from the other tables in the next round. Another tournament format, Elimination Blackjack, drops the lowest-stacked player from the table at pre-determined points in the tournament. Good strategy for blackjack tournaments can differ from non-tournament strategy because of the added dimension of choosing the amount to be wagered. As in poker tournaments, players pay the casino an initial entry fee to participate in a tournament, and re-buys are sometimes permitted.
Some casinos, as well as general betting outlets, provide blackjack among a selection of casino-style games at electronic consoles. Video blackjack game rules are generally more favorable to the house; e.g., paying out only even money for winning blackjacks. Video and online blackjack games generally deal each round from a fresh shoe (i.e., use an RNG for each deal), rendering card counting ineffective in most situations.
Blackjack is a member of family of traditional card games played recreationally worldwide. Most of these games have not been adapted for casino play. Furthermore, the casino game development industry actively produces blackjack variants, most of which are ultimately not adopted by casinos. The following are the most prominent and established variants in casinos.
Examples of local traditional and recreational related games include French Vingt-et-un ("Twenty-One") and German Siebzehn und Vier ("Seventeen and Four"). Neither game allows splitting. An ace only counts as eleven, but two aces count as a blackjack. It is mostly played in private circles and barracks. The popular British member of the Vingt-Un family is called Pontoon, the name being probably a corruption of "Vingt-et-un".
In 2002, professional gamblers around the world were invited to nominate great blackjack players for admission into the Blackjack Hall of Fame. Seven members were inducted in 2002, with new people inducted every year after. The Hall of Fame is at the Barona Casino in San Diego. Members include Edward O. Thorp, author of the 1960s book Beat the Dealer; Ken Uston, who popularized the concept of team play; Arnold Snyder, author and editor of the Blackjack Forum trade journal; and Stanford Wong, author and popularizer of "Wonging".