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.^[1] For the side bet, the player will typically put up an additional wager alongside his or her main bet and can win or lose the side bet, regardless of the main game result. The house edge for side bets is usually much higher than for the main game.

Notes

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 probability (nearly one-third) to be ten-valued, giving the dealer a blackjack and almost certainly results in a loss for the player. (Thus,the expression, “ace in the hole”). 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 have a value of ten (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 dealer causes the proportion of the remaining cards that are valued at ten to be higher. Even so, the bet is generally to be avoided, as 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 or she has an edge (e.g., 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 if the player simply observes the other cards on the table – for an initial hand, 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 neither of their two initial cards is a ten, then 16 of 47 remaining cards are tens – better than 1 in 3, making the insurance bet a good one.^[1]

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 only a slightly different bet; the difference being that the player must have sufficient funds to insure blackjack if even money is not offered. Taking even money is generally a poor choice, because one of the player’s two cards is a ten, so the proportion of tens remaining in the deck is lower.

In casinos in which 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 hole card over a small mirror or electronic sensor on the tabletop in order to check whether he has a blackjack. This practice minimizes the risk of inadvertently revealing the hole card, which may give the sharp-eyed player a considerable advantage.

Notes

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In most non-U.S. casinos, a ‘no hole card’ game is played, meaning that the dealer does not draw nor consult his 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 A’s 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.

In some places, such as some casinos in Australia and New Zealand, 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 basic strategy as the hole card game, and the same advantage.

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This rule, often called the Reno 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.

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After a player has split a pair in blackjack, most casinos allow him or her to “double down” on either or both of the new two-card hands. This is called “double after split” and provides an advantage to the player of about 0.12%.

After splitting aces, one 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. Allowing the player to hit hands resulting from split aces reduces the casino edge by about 0.13%; allowing resplitting aces reduces the edge by about 0.03%. While resplitting aces is not uncommon, houses that allow the player to hit split aces are extremely rare.

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If the player splits a pair other than aces and a third card of that value appears, the player can usually split again (or “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″).

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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 should 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. With early surrender, a player is more likely to surrender against a dealer Ace.

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The number of decks used has a major effect on the player’s chance of winning, because it affects the house advantage. 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 greater 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 statistically the player should get paid at 3:2 more often in the single deck game.

When single deck blackjack is offered, it is generally offered with more restrictive rules that favor the house. For illustrative purposes, the statistics below all use the same rules: double after split, resplit to four hands, one card to 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 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.

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