Blackjack Strategy Calculator
Calculate optimal blackjack moves based on your hand and dealer upcard using basic strategy. Enter values for instant results with step-by-step formulas.
Reviewed by Daniel Agrici, Founder & Lead Developer
Formula
Optimal Action = BasicStrategy[HandType][HandTotal][DealerUpcard]
Basic strategy is derived from computer simulations of millions of blackjack hands. For each combination of player hand (hard, soft, or pair) and dealer upcard, the expected value of every possible action is calculated, and the action with the highest expected value is selected.
Worked Examples
Example 1: Hard 16 vs Dealer 10
Problem:You hold a 10 and a 6 (hard 16) against a dealer showing 10. What should you do?
Solution:Hand type: Hard 16\nDealer upcard: 10\nBasic strategy lookup: Hard 16 vs 10 = Surrender (R)\nIf surrender unavailable: Hit (H)\nDealer bust probability with 10: 23.2%\nPlayer bust if hitting: 61.5%\nExpected loss standing: ~48%\nExpected loss hitting: ~54%\nExpected loss surrendering: 50% (but you save half your bet)
Result:Optimal Play: Surrender (or Hit if unavailable) | Dealer bust chance: 23.2%
Example 2: Soft 18 vs Dealer 9
Problem:You hold an Ace and 7 (soft 18) against a dealer showing 9. What is the correct play?
Solution:Hand type: Soft 18 (Ace + 7)\nDealer upcard: 9\nBasic strategy lookup: Soft 18 vs 9 = Hit (H)\nThis is counterintuitive since 18 seems strong\nBut dealer average hand with 9 showing is ~18.5\nHitting cannot bust (soft hand reverts to hard if over 21)\nHitting improves the hand more often than standing holds
Result:Optimal Play: Hit | Standing on soft 18 vs 9 is a common mistake
Frequently Asked Questions
What is basic blackjack strategy and does it really work?
Basic strategy is a mathematically optimal set of decisions for every possible blackjack hand combination. It was first developed in the 1950s by Roger Baldwin and later refined by Edward Thorp using computer simulations of millions of hands. Basic strategy reduces the house edge to approximately 0.5 percent, making blackjack one of the best odds games in the casino. Without basic strategy, the average player faces a 2 to 5 percent house edge. The strategy accounts for the probability of every possible card draw, the dealer rules, and expected values of hitting, standing, doubling, and splitting. While it does not guarantee winning any individual hand, it maximizes your long-term expected return over thousands of hands played.
When should you double down in blackjack?
Doubling down is optimal when you have a mathematical advantage on the next card. The strongest double down situation is a hard 11 against any dealer card, because you have the best chance of making 21. With hard 10, double against dealer 2 through 9. With hard 9, double against dealer 3 through 6. For soft hands containing an ace, double with soft 16 through 18 against dealer 4 through 6, and soft 17 against dealer 3 through 6. Never double down on hard 12 or higher because the bust risk is too great. Doubling down effectively lets you double your bet when the odds temporarily favor you, which is why knowing the correct situations is crucial for reducing the overall house advantage.
Should you always split aces and eights in blackjack?
Yes, splitting aces and eights is one of the most fundamental rules of basic strategy. Always split aces because each ace gives you a starting hand of 11, the strongest starting position for any hand. Always split eights because a hard 16 is the worst possible hand in blackjack, and splitting gives you two chances to build competitive hands starting from 8. Conversely, never split tens because 20 is already an excellent hand that wins the vast majority of the time. Never split fives because a hard 10 is a strong doubling opportunity. Pairs of fours should generally not be split either, as a hard 8 is better played as a single hand. Splitting decisions for other pairs depend on the dealer upcard.
How does the number of decks affect blackjack odds?
The number of decks significantly impacts the house edge in blackjack. A single-deck game with standard rules has a house edge of about 0.17 percent, while an eight-deck shoe increases it to approximately 0.65 percent. More decks reduce the effectiveness of doubling down on 11 because there are proportionally fewer tens in the remaining cards relative to total cards. The probability of natural blackjack decreases slightly with more decks. Card counting becomes more difficult with more decks because individual card removals have less impact on the remaining composition. Most casinos use six or eight decks specifically to combat card counting and increase their edge. However, basic strategy adjustments for multi-deck games are minor, and the core strategy decisions remain largely the same.
References
Reviewed by Daniel Agrici, Founder & Lead Developer · Editorial policy