Blackjack: rules, odds and basic strategy

Blackjack has one of the lowest house edges of the common casino table games, but only if you play it properly and pick a table with good rules. With a 3:2 payout on blackjack, the dealer standing on soft 17 and doubling after splits allowed, basic strategy brings the edge down to about 0.5%. Play by feel, or sit at a 6:5 table, and that number rises quickly.

How blackjack works

1. You place a bet. You and the dealer each get two cards. Usually one dealer card is face up.
2. Cards 2 to 10 count at face value, jacks, queens and kings count 10, and an ace counts 1 or 11.
3. An ace plus a ten-value card on your first two cards is a blackjack. It beats any other 21.
4. You act on your hand: hit (take a card), stand, double (double your bet and take exactly one card), split a pair into two hands, or surrender half your bet where allowed.
5. Go over 21 and you bust and lose, even if the dealer busts later.
6. The dealer then plays by fixed rules: draw to 16, stand on 17 or more.

A hand containing an ace counted as 11 is soft. Soft 17 (for example A-6) matters because tables differ on what the dealer does with it.

Dealer rules: S17 and H17

At an S17 table the dealer stands on soft 17. At an H17 table the dealer hits it. Hitting soft 17 helps the dealer and costs you about 0.22 percentage points, according to the Wizard of Odds rule table. The rule is printed on the felt or in the game's help screen.

Payouts: 3:2 versus 6:5

A standard blackjack pays 3:2: £15 on a £10 bet. Some tables pay 6:5: £12 on the same bet. That £3 difference on every blackjack adds about 1.39 percentage points to the house edge, enough to make a 0.5% game close to a 2% game. Even money on a blackjack (1:1) is worse again, at about 2.27 points.

Doubling, splitting and surrender

Doubling lets you put more money out when you are the favourite, usually on 10 or 11 against a weak dealer card. Some tables restrict doubling to 9 to 11 or 10 to 11, which raises the edge.

Splitting turns a pair into two hands, each with its own bet. Aces and eights are always split. Tens are never split. Double after split (DAS) lets you double on a hand made by splitting; losing it costs about 0.14 points.

Late surrender lets you give up half your bet after the dealer checks for blackjack. Used only on the right hands (16 against 9, 10 or ace; 15 against 10), it is worth about 0.08 points to you.

Insurance: why it is a bad bet

When the dealer shows an ace, you are offered insurance, a side bet up to half your stake that pays 2:1 if the dealer has blackjack. For insurance to break even, a ten-value card would need to be under the ace a third of the time.

In an eight-deck shoe, after the dealer's ace is removed, 128 of the remaining 415 cards are tens: a 30.8% chance. The bet returns 3 × 128 ÷ 415 = 0.925 for every 1 staked, an edge of about 7.5%. In six decks (96 tens among 311 cards) it is about 7.4%. These are our calculations from the card counts, ignoring the cards in your own hand. "Even money" on your own blackjack is the same bet in disguise. Only a card counter who knows the shoe is rich in tens should ever take it.

Basic strategy

Basic strategy is the mathematically best play for every combination of your hand and the dealer's up card. It does not remove the house edge. It makes it as small as it can be without tracking cards.

The chart below is for four to eight decks, dealer stands on soft 17, double after split allowed, late surrender allowed. It matches the Wizard of Odds strategy for those rules. If surrender is not offered, hit where the chart says Rh.

Key: H = hit, S = stand, D = double (hit if you cannot), Ds = double (stand if you cannot), P = split, Rh = surrender (hit if you cannot).

A few patterns make it easier to remember. Stand on stiff hands (12 to 16) when the dealer shows 2 to 6, except 12 against 2 or 3. Hit them against 7 or higher. Never take insurance. At an H17 table a handful of plays change, so use a chart for those rules.

How the rules move the house edge

The Wizard of Odds lists each rule's effect against a baseline of eight decks, S17 and DAS:

A game with liberal rules (S17, double on any two cards and after splits, resplit aces, late surrender) comes in at about 0.28%, according to the Wizard of Odds house edge comparison.

Card counting online: the reality

Counting works by tracking the ratio of high to low cards left in a shoe and betting more when it favours you. Online, that is close to impossible:

• RNG blackjack reshuffles virtually. As a reader question on the Wizard of Odds puts it, most online casinos shuffle after every hand, so there is nothing to count.
• Continuous shuffling machines, used at some land-based and live tables, return discards to the shoe constantly. The Wizard's advice to counters is to avoid them.
• Live dealer blackjack deals from a shoe, so counting is possible in principle, but the casino decides how much of the shoe is dealt before a reshuffle. Treat counting as a theory, not a plan.

Side bets

Side bets carry far higher edges than the main game. The 21+3 and Perfect Pairs figures are from the Wizard of Odds; the insurance figure is our own calculation (see above):

Pay tables vary by table and studio, and small changes move the edge a lot. Check the help screen.

Playing online: RNG, live and RTP versions

RNG blackjack is dealt by a random number generator, usually allows demo play, and lets you play at your own pace. Live blackjack is dealt by a real dealer on camera; see our live dealer games guide and studio pages such as Evolution and Playtech. Rules differ between versions, so read the help screen for the payout, soft 17 rule and doubling rules before you play. Our RTP and volatility guide explains how house edge and RTP relate.

Related games: baccarat, casino poker games and video poker.

Where to play

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