The master chart used for learning blackjack basic strategy was developed for a multiple-deck game in which the dealer stands on a soft 17. It should not be applied in all situations, because both of these factors the number of decks and the rules that affect the dealer have an impact on possible outcomes.
Single Deck Blackjack
In all blackjack, there is a definite limit to the number of cards in a deck and when all cards of a certain value are drawn, the likelihood of their appearing, when compared to a card of any other value, drops with each hand. These differences can be significant.
The maximum number of hits that must be computed will be decreased when all possible low cards (aces and twos) are depleted. A dealer’s hand of 5 (a three and a two) will need to take a maximum of 9 hits in a multiple-deck game (3 hits of two, followed by six aces) but only eight hits in a single-deck game (three hits of two, four aces, then a three).
Also, as cards are dealt with the player’s and dealer’s hand, it becomes less likely that any unknown card will have those values. For example, if the dealer’s upcard is a five, it is 1.9% less any unknown card will have a value of five (3/51 as opposed to 4/51), if no other fives are showing. The possibility that the initial value of the dealer’s hand is a 10 is slightly less than any other value, and the possibility that any player’s hand will contain a five-value card is slightly less.
For the same reason, a player is 4.00% likely to be dealt a five after splitting a pair of fives (since two are already consumed, there are only two remaining in 50 unknown cards). Further, if the player has a pair of fives and the dealer’s upcard is five, (1 among 49 unknown cards) there is only a 2% likelihood of an unknown card being a five.
If a five shows as any hit on the player’s or dealer’s hand when the player has a pair of fives and the dealer has a five showing, there is a 0% chance that a five will appear again at all, so the odds of remaining hits are 1 in 12 instead of 1 in 13. The net effect can be dramatic on the possible outcome of each hand.
In a multiple-deck game, these odds are diluted to the point of insignificance. In a two-deck game, each five dilutes the deck by only 1/103 (0.97%) and in eight decks, only 1/415 (0.24%). At this point, the effects of dilution are minuscule and will have a negligible effect on the outcomes
Single Deck Blackjack Strategy Chart
To account for these differences, the player should use the appropriate blackjack chart for the game he is entering:
Note: if doubling is not possible in instances where it is indicated,hit instead—except for doubles marked with an asterisk (*D), where a hand that cannot be doubled should be stood.
Rather than memorizing all four charts, it’s easiest to memorize the chart for the most common game the player will enter, and note the differences.
Since most tables offer a multiple-deck game in which the dealer stands of soft 17, here are the differences from that perspective:
Blackjack Basic Strategy Single Deck
- Double all eights (including paired fours) against 5 or 6
- Double nines against a deuce
- Do not surrender soft 15 against 10
- Do not surrender soft 16 against 9
- Double soft 13 or 14 against a four
- Double soft 17 against a deuce
- Double soft 19 against a six
- Split a paired 4 against a 4
- Do not split deuces against a three
- Split sixes against a seven
- If the dealer stands on soft 17, double 11 against an ace.
Dealer Hits Soft 17
In games where the dealer hits a soft 17, the outcome of any low or soft hand are offset. When a hit is taken on soft 17, there is a 21.21% chance the hand will bust, and a 44.57% chance the resulting hand will he higher than 17 (versus a 0% chance of either if the dealer stands).
This will affect the probably outcomes of any dealer’s hand in which a soft 17 may be persent (an ace or a six showing), or any hand in which a hit at any time is likely to produce a soft 17 (all hands showing two through five).
Regardless of the number of decks used, hitting on soft 17 will alter the chances for the dealer’s outcome in almost half (46.15%) of all situations.
When a dealer hits on soft 17
- Double 11 against an ace.
- Surrender 15 and 17 against an ace.
- Double soft 19 against a 6
- If four decks are used—double soft 18 against a deuce and surrender paired eights if you cannot split them.
- In a single-deck game, split paired threes against an eight.