Blackjack is unusual among casino games: the player's decisions change the house edge. Played badly, it can be one of the more expensive games on the floor. Played with basic strategy, it is one of the cheapest. This entry explains what basic strategy is and how much the table rules matter.
What basic strategy is
Basic strategy is the mathematically best decision (hit, stand, double, split or surrender) for every combination of your hand and the dealer's visible card, assuming you do not track which cards have already been played. It was worked out by computer analysis decades ago and is usually presented as a chart.
A few of its best-known rules:
| Your hand | Dealer shows | Basic strategy |
|---|---|---|
| Hard 16 | 7 to ace | Hit (or surrender if allowed) |
| Hard 12 | 4 to 6 | Stand |
| 11 | 2 to 10 | Double |
| Pair of 8s | Any card | Split |
| Pair of 10s | Any card | Stand |
| Soft 18 (ace and 7) | 9, 10 or ace | Hit |
Charts vary slightly with the number of decks and the rules. Use the chart for the exact game you play.
The house edge with basic strategy
With basic strategy, most blackjack games have a house edge of between about 0.5% and 1%, according to commonly cited figures. That compares with 2.70% for single-zero roulette and 1.06% for the banker bet in baccarat. See House Edge of Every Casino Game, Ranked.
Without basic strategy, the edge is higher, because typical mistakes, such as standing on 12 against a dealer 2 or never doubling, give money away.
Rules that change the edge
| Rule | Effect on the house edge |
|---|---|
| Blackjack pays 6 to 5 instead of 3 to 2 | Adds about 1.4% |
| Dealer stands on soft 17 instead of hitting | Lowers it by about 0.2% |
| More decks in the shoe | Raises it slightly |
| Surrender allowed | Lowers it slightly |
| Doubling after splitting allowed | Lowers it slightly |
Worked example: The 6 to 5 rule in numbers. On a 10-unit bet, a natural blackjack pays 15 at 3 to 2 but only 12 at 6 to 5. Blackjacks come up roughly once every 21 hands, so the lost 3 units add up to an extra edge of about 1.4%, enough to make a 0.5% game cost almost four times as much.
Key point: Read the table sign before sitting down. "Blackjack pays 3 to 2" and "dealer stands on soft 17" are the two rules worth looking for first.
What about card counting?
Card counting tracks the ratio of high to low cards left in the shoe and raises bets when it favours the player. It is not illegal, but casinos can refuse play, shuffle more often or use continuous shuffling machines that make it ineffective, and online blackjack usually reshuffles every hand. For most players it is not a practical way to beat the game.
Watch out: Basic strategy reduces the house edge; it does not remove it. Over many hands, the expected result is still a loss of the amount bet times the edge.
Insurance
When the dealer shows an ace, you may be offered insurance. Basic strategy says decline it: in standard games the bet carries a higher house edge than the main hand.
For more on how edges translate into session results, see Volatility and Session Length.
- Basic strategy is the best decision for every hand and dealer card, without counting cards.
- With it, blackjack's house edge is typically about 0.5% to 1%.
- A 6 to 5 payout adds about 1.4%; a dealer standing on soft 17 lowers the edge by about 0.2%.
Sources
- Blackjack — Wikipedia: rules, basic strategy and house edge
- Card counting — Wikipedia
18+ only. No betting system changes the house edge. See our Responsible Gambling page.
RTP Data explains the mathematics of casino games, with every figure sourced or worked out in the text.