In casino blackjack, the dealer faces one to seven players from behind a kidney-shaped table. Each player plays his hand independently against the dealer. At the beginning of each round, the player places a bet in the "betting box" and receives an initial hand of two cards

In casino blackjack, the dealer faces one to seven players from behind a kidney-shaped table. Each player plays his hand independently against the dealer. At the beginning of each round, the player places a bet in the "betting box" and receives an initial hand of two cards. The object of the game is to get a higher card total than the dealer, but without going over 21 which is called "busting" or "too many." (The spot cards count 2 to 9; the 10, jack, queen, and king count as ten; an ace can be either 1 or 11 at the player's choice). The player goes first and plays his hand by taking additional cards if he desires. If he busts, he loses. Then the dealer plays his/her hand. If the dealer busts, he/she loses to all remaining players. If neither busts, the higher hand total wins. In case of a tie, no one wins - the hand is a "push" and all bets are returned. It is possible for the dealer to lose to some players but still beat other players in the same round.

Example of a Blackjack game. The top half of the picture shows the beginning of the round, with bets placed and an initial two cards for each player. The bottom half shows the end of the round, with the associated losses or payoffs.

Cards are dealt in three ways, either from one or two hand-held decks, from a box containing four to eight decks called a "shoe," or from a shuffling machine. When dealt by hand, the player's two initial cards are face-down, while the dealer has one face-up card called the "upcard" and one face-down card called the "hole card." (In European blackjack, the hole card is not actually dealt until the players all play their hands.) When dealt from a shoe, all player cards are normally dealt face-up, with minor exceptions. It shouldn't matter to the player whether his cards are dealt face-down or face-up since the dealer must play according to predetermined rules. If the dealer has less than 17, she must hit. If the dealer has 17 or more, she must stand (take no more cards), unless it is a "soft 17" (a hand that includes an ace valued as "11," for example a hand consisting of Ace+6, or Ace+2+4). With a soft 17, the dealer follows the casino rules printed on the blackjack table, either to "hit soft 17" or to "stand on all 17's."

The highest possible hand is a "blackjack" or "natural," meaning an initial two-card total of 21 (an ace and a ten-value card). A player blackjack is an automatic winner unless the dealer also has blackjack, in which case the hand is a "push" (a tie). When the dealer upcard is an ace, the player is allowed to make a side bet called "insurance," supposedly to guard against the risk that the dealer has a blackjack (i.e., a ten-value card as his or her hole card). The insurance bet pays 2-to-1 if the dealer has a blackjack. Whenever the dealer has a blackjack, she wins against all player hands except those that also have a blackjack (which are a "push").

The minimum and maximum bets are posted on the table. The payoff on most bets is 1:1, meaning that the player wins the same amount as he bets. The payoff for a player blackjack is 3:2, meaning that the casino pays $3 for each $2 originally bet. (There are many single-deck games which pay only 6:5 for a blackjack.)

Player decisions

After receiving his initial two cards, the player has four standard options: he can "Hit," "Stand," "Double Down," or "Split a pair." Each option requires the use of a hand signal. At some casinos or tables, the player may have a fifth option called "Surrender."

• Hit: Take another card.

  signal: (handheld) scrape cards against table; (face up) touch finger to table or wave hand toward himself

• Stand: Take no more cards, also "stick" or "stay".

  signal: (handheld) slide cards under bet; (face up) wave hand horizontally

• Double down: On his first two cards, the player may "double down," i.e., "double" his bet and receive only one card. To do this he moves a second bet equal to the first into the betting box next to his original bet. (If desired, the player is usually allowed to "double down for less," although this is generally not a good idea as the player should only double in favorable situations but should then increase the bet as much as possible.)

  signal: place additional chips next to (not on top of) original bet

• Split a pair: If his first two cards are a "pair," meaning two cards of the same value, the player can "split the pair." To do this, he moves a second bet equal to the first into the betting box next to his original bet. The dealer splits the cards to create two hands, placing one bet with each hand. The player then plays two separate hands.

  signal: place additional chips next to (not on top of) original bet.

• Surrender: Some casinos offer a fifth option called "Surrender." After the dealer has checked for blackjack, the player may "surrender" by giving up half his bet and not playing out the hand.

  signal: There is no commonly accepted hand signal; it is just done verbally.

The reason for requiring hand signals is to assist the "eye in the sky," a person or video camera located above the table but concealed behind one-way glass. It is used in order to protect the casino against dealers or players who cheat. (It may also be used to protect the casino against card-counters, even though card-counting is not illegal.)

The player can take as many hits as he wants as long as the total is not above hard-20. However, if he busts, he loses that hand. After all the players have finished making their decisions, the dealer then reveals his or her hole card and plays out his or her hand according to predetermined rules.

Rule variations and the "house advantage"

The blackjack player will encounter many rule variations which affect the house advantage and therefore affect his chances of winning. Some rules are determined by law or regulation, others by the casino itself. Not all rules are posted, so the player may have to ask either beforehand or when the situation occurs. Over 100 variations exist.

The casino has a "house advantage" at blackjack just as it does at any other casino game. If a particular casino game has a house advantage of 5%, it means that - over the long run - the casino will win about 5% of any initial bet. As long as the blackjack player uses the best possible strategy (a strategy which is known as "Basic Strategy"), the house advantage in blackjack is usually less than 1%. This is very favorable to the player compared to other casino games. Of course, many blackjack players do not know Basic Strategy or do not follow it, so the true house advantage in those cases is much higher.

Dealer hits soft 17?

Each casino has a rule about whether or not the dealer hits soft 17, a rule which is printed on the table itself. In the "S17" game, the dealer stands on all 17s. In the "H17" game, the dealer hits on soft 17s. Of course, the dealer always stands on hard 17s. In either case, the dealer has no choice; she either must or must not hit. The "Hit soft 17" game is substantially less favorable to the player with about a 0.2% higher house advantage.

Number of decks

The number of decks used has a major effect on the player's chance of winning, because it affects the house advantage. (See comparative statistics below.) All things being equal, fewer decks are always more favorable for the basic strategy player. One cause of this is that player blackjack is slightly more likely in single deck blackjack (because blackjack requires two different cards, by removing a card of one type (e.g., a Ten), getting one of a different type (e.g. an Ace) is more likely - and the effect is much bigger in a single deck game than in a multi-deck game), and if the player does have blackjack, the dealer is significantly less likely to have blackjack as well (which is a push), meaning that the player will get paid at 3:2 more often in the single deck game.

In reality, multi-deck games almost always have otherwise better rules than single-deck games. However, card counting is much more effective for single deck games. For illustrative purposes, the statistics below all use the same rules—double after split, no resplits, one card to split Aces, no surrender, double on any two cards, original bets only lost on dealer Blackjack, dealer hits soft 17. The single deck game is much better than double deck, which is significantly better than four decks, while from six decks and up there is very little difference.

Surrender

Some casinos offer a favorable option called "surrender," which allows the player to give up half his bet and not play out the hand. This option is sometimes referred to as "late" surrender because it occurs after the dealer has checked his or her hole card for a blackjack. (When casinos first opened in Atlantic City, the surrender option was available before the dealer checked for blackjack - a rule highly advantageous to the player - but this "early surrender" option soon disappeared.) Early Surrender variations still exist in several countries.

The player will only surrender on the very worst hands, because having even a 25% chance of winning will result in a better average return than giving up half of his bet. See strategy table below for details. With early surrender, a player will surrender very often against a dealer Ace - even including hard 17.

Resplit to nn

If the player splits a pair other than aces and a third card of that value appears, the player can usually resplit by putting up another bet equal to the original bet. Then there will be three bets on the table and three separate hands. Some casinos allow unlimited resplitting of cards other than aces, while others may limit it to a certain number of hands, such as four hands (for example, "resplit to 4").

 Hit/resplit split aces

After splitting aces, the usual rule is that only one card will be dealt - the player cannot split, double or even hit. Rule variants include allowing resplitting aces and allowing the player to hit split aces. Allowing the player to hit Aces reduces the casino edge by about 0.13%, allowing resplitting Aces reduces the edge by about 0.03%.

 Double after split

After splitting a pair, some casinos allow the player to "double down" on each of the new two-card hands. This is called "double after split" (DAS) and provides an advantage to the player of about 0.12%.

 Double on 9/10/11 or 10/11 only

Often called "Reno" rules, this rule restricts the player to doubling down only on an initial player total of 10 or 11 (sometimes 9, 10, or 11 - more common in Europe). It prevents doubling on soft hands such as soft 17 (ace-6), and is unfavorable for the player. It increases the house advantage by between 0.09% (8 decks) and 0.15% (1 deck) for the 9-11 rule, and between 0.17% (8 decks) and 0.26% (single deck) for the 10-11 rule. These numbers can vary due to interaction with other rules.

European no-hole-card rule

In most non-U.S. casinos, a 'no hole card' game is played. This means that there is no dealer hole card. This affects the player's strategy when deciding whether to double and/or split since a dealer Blackjack will result in the loss of the split and double bets. 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.

In some places, if the dealer is later found to have blackjack, the player loses only his original bet but not any additional bets (doubles or splits). This has the same advantage as the usual game, and as such does not change basic strategy.

Altered payout for blackjack

In some places, a blackjack pays only 6:5 or even 1:1 instead of the usual 3:2. This is the most unfavorable variation, increasing the house edge significantly more than any other player restriction. 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. The 1:1 payout for video blackjack is a key reason why it has never approached the table version in terms of popularity. The 6:5 rule is most commonly employed on table blackjack at single deck games - which are otherwise the most attractive game for a basic strategy player.

 Dealer wins ties

This is catastrophic to the player, though rarely used in standard Blackjack. It is sometimes seen in "blackjack-like" games.

Six card charlie

With this rule, the player wins if six cards have been drawn without busting. It may or may not win if the dealer has a Blackjack. This rule adds about 0.16% to the player edge if an altered strategy is used. The advantage is less with normal Basic Strategy.

 Insurance

If the dealer's upcard is an ace, the player is offered the option of taking Insurance before the dealer checks his or her 'hole card'.

Insurance is a side bet of up to half the original bet placed on a special portion of the table usually marked "Insurance Pays 2 to 1". This side bet is offered only when the dealer's exposed card is an ace. The idea is that the dealer's second card has a fairly high probablility (nearly one-third) to be ten-valued, giving the dealer a blackjack and a certain loss for the player. It is attractive (although not necessarily wise) for the player to insure against this possibility by making an "insurance" bet, which pays 2-to-1 if the dealer has a blackjack, in which case the "insurance proceeds" will make up for the concomitant loss on the original bet. The insurance bet is lost if the dealer does not have blackjack, although the player can still win or lose on the original bet.

Insurance is a poor bet for the player unless he is counting cards, because in an infinite deck 4/13 of the cards are "tens" (10, J, Q, or K) (and 9/13 therefore are not), so the theoretical return for an infinite deck game is 4/13 * 2 * bet - 9/13 * bet = -1 /13 * bet, or -7.69%. In practice, the average house edge will be lower than this, because by eliminating even one non-ten card from the shoe (the dealer's Ace), the proportion of the remaining cards that are tens is higher. Even so, the bet is generally to be avoided, as the the house's average edge is still more than 7%.

A player who is counting cards can keep count of the remaining tens in the shoe, and use it to make insurance bets only when he has an edge (i.e. when more than one third of the remaining cards are tens). In addition, in a multi-hand single deck game, it is possible for insurance to be a good bet simply by observing the other cards on the table - if the dealer has an Ace, then there are 51 cards left in the deck, of which 16 are tens. However, if there are as few as 2 players playing, and none of their two initial cards are tens, then that means that 16 out of 47 remaining cards, are ten - better than 1 in 3, and so the insurance bet is a good one.

When the player has blackjack and the dealer has an ace, the insurance bet may be offered as "even money", meaning that the player's blackjack is paid immediately at 1:1 before checking the dealer's hand. 'Even money' is just a way of expressing the actual payout on the insurance bet, given that the player has blackjack, it is not a different bet, and taking even money is generally even worse than average, because one of the player's two cards is tens, so the proportion of tens remaining in the deck is lower.

In casinos where a hole card is dealt, a dealer who is showing a card with a value of Ace or 10 may slide the corner of his or her hole card over a small mirror or electronic sensor on the tabletop in order to check whether she has a blackjack. This practice minimizes the risk of inadvertently revealing the hole card, which may give the sharp-eyed player a considerable advantage.

Side bets

Some casinos offer a side bet with their blackjack games. Examples include side bets based on getting three 7s, a three card poker-style bet, a pair, and many others. For the sidebet, the player will typically put up an additional wager alongside his main bet. Typically the player can win or lose the sidebet, regardless of the main game result. As there is little or no strategy involved, the house edge for side bets is usually much higher than the main game (which requires accurate play).