Blackjack is the primary game for bonuses due to its low house edge and low standard deviation (variance).
Blackjack hands are scored according to the sum of card values. For example, a hand composed of a 4, 5, and 6 is scored as 4+5+6=15. Face cards each have a value of 10. Aces can be valued as either 1 or 11, so an ace and 7 could be scored as either a 8 or a 18. The objective in blackjack is to have the highest card sum that does not exceed 21. A sum of greater than 21 is called a bust. If the player busts, he loses his bet, regardless of the dealer hand. A 2-card 21 is known as a “blackjack” and is the highest ranking hand. The player receives a bonus for having a blackjack. Blackjacks pay 3:2, while other wins pay 1:1.
After placing a bet, the player and dealer are each given two cards. One of the dealer’s two cards is face up and visible to the player. Under standard rules, if the dealer has an ace or 10-point card showing, he will peek for a possible blackjack. If the dealer has an ace showing, the player has the opportunity to buy “insurance” against the blackjack. Insurance pays 2:1 if the dealer’s remaining card is a 10 or face card to form a blackjack.
If the dealer does have a blackjack, the hand will end. If the dealer does not have a blackjack, then the player must decide how to play his hand. Possible options are listed below:
- Stand: Stop playing. If you think that your hand is enough to win, or it is too risky to draw further cards.
- Hit: Draw an other card. We have this opportunity until we either reach 21, or exceed it (bust).
- Double: The situation is so favourable, that we would like to play for double money. Important, that when doubling, we are allowed to draw ONLY ONE further card.
- Split: If we have 2 cards of the same value, we have the opportunity to split them to 2 hands, and play each separately. It is needed to put in an other bet equal to the initial, for the second hand.
After we completed our hand, the dealer plays his hand as well, the software decides who wins, and we can start another hand. The dealer always plays according to rules. It is essential to know these rules well, as it determines our optimal strategy.
A little mathematics
House edge is existing in Blackjack, because the dealer has a hole card. Thus we have to make decisions upon imperfect infomation. Every time we make a different decision than we would make if we knew the dealer’s hole card, theoretically we lose, even if we actually win the hand.
So we have to make assumptions about the dealer’s hand. We also have to make an assumption about our next card, if we decide to hit. The expected value of the next card in either cases is the mean of the values of the possible cards left in the deck. If we play a single deck game, it is significant if we can see a King down, as it reduces the chance of hitting a king quite significantly. But if we play at least a 4-deck game, this does not make such a big difference, so we can calculate as any card has the same probability. So in a typical 8-deck game, with a 10 shown, the dealer’s hole card’s expected value is 7 (2+3+4+5+6+7+8+9+10+10(J)+10(Q)+10(K). Aces are not counted here, as in most games, the dealer peaks for Blackjack). This quite simple principle is the basis of the below strategy tables.
House edge of Blackjack varies from 0% to about 1,5%. Single deck Blackjacks have the lowest HE, about 0.1%. If allowed, play these (they are called Classic Blackjack in Microgaming casinos). Standard Blackjack (8 decks, dealer stand on soft 17, no surrender) has a House Edge of 0.5%. These are the rules in the Playtech software. The standard deviation of Blackjack is about 1.15, which is one of the lowest values in the casino.
Never accept insurance.
Below you can see the tables which show the optimal strategies for Blackjack.