As in all casino games, the house has a statistical advantage over the players that will play itself out in the long run. But because blackjack, unlike other games, has an element of player choice, players can actually reduce the casino advantage to a small percentage by playing what is known as basic strategy. This strategy determines when to hit and when to stand, and also determines when doubling down or splitting is the correct action. Basic strategy is based on the player’s point total and the dealer’s visible card. There are slight variations in basic strategy depending on the exact house rules and the number of decks used. Under the most favorable conditions (single deck, downtown Las Vegas rules), the house advantage over a basic strategy player can be as low as 0.16%. Indeed, casinos offering special rules like surrender and double-after-split may actually be offering a positive expectation to basic strategy players; they are counting on players making mistakes to make money.
The following rules are beneficial to the player:
- Doubles are permitted on any two-card hand except a blackjack.
- Doubles are permitted after splitting.
- Early surrender; the ability to forfeit half your wager against a face or ace before the dealer checks for blackjack.
- Normal (aka “late”) surrender.
- Resplitting Aces.
- Drawing more than one card against a split Ace.
- Five or more cards with the total still no more than 21 as an automatic win (a “Charlie”)
The following rules are detrimental to the player:
- Less than 3:2 payout on blackjacks (6:5 and even 1:1 payouts have become common, especially in single-deck games, in Las Vegas since about 2003)
- Dealer hits on soft seventeen (ace, six)
- Splitting a maximum of once (to two hands)
- Double down restricted to certain totals, such as 9-11 or 10,11
- Aces may not be resplit
- No-Peek (European) blackjack—player loses splits and doubles to a dealer blackjack
- Player losing ties
Basic strategy tables
|Your hand||Dealer’s face-up card|
The above is a basic strategy table for the most common 6- to 8-deck, Las Vegas Strip rules. Specifically: dealer hits on soft 17, double after split allowed, multiple split aces, one card to split aces, blackjack pays 3:2, and (optionally) late surrender. Key:
- S = Stand
- H = Hit
- D = Double
- SP = SPlit
- Rh = suRrender if allowed, otherwise Hit
- Rs = suRrender if allowed, otherwise Stand
- Rsp = suRrender if allowed, otherwise SPlit
There are well-established techniques other than card counting that can swing the advantage of casino 21 towards the player. All such techniques are based on the value of the cards to the player and the casino, as originally conceived by Edward O. Thorp. One such technique, mainly applicable in multi-deck games (aka shoes), involves tracking groups of cards (aka slugs, clumps, packs) during the play of the shoe, following them through the shuffle and then playing and betting accordingly when those cards come into play from the new shoe. This technique, which is admittedly much more difficult than straight card counting and requires excellent eyesight and powers of visual estimation, has the additional benefit of fooling the casino people who are monitoring the player’s actions and the count, since the shuffle tracker could be, at times, betting and/or playing opposite to how a straightforward card counter would.
Arnold Snyder’s articles in Blackjack Forum magazine were the first to bring shuffle tracking to the general public. His book, The Shuffle Tracker’s Cookbook, was the first to mathematically analyze the player edge available from shuffle tracking based on the actual size of the tracked slug.
Other legal methods of gaining a player advantage at blackjack include a wide variety of techniques for gaining information about the dealer hole-card or the next card to be dealt.