Blackjack Basic Strategy — The Complete Guide

Blackjack is the one casino game where your decisions directly and measurably affect the outcome. Unlike roulette or slot machines, every choice you make at the blackjack table — whether to hit, stand, double, or split — has a mathematically correct answer. That answer is called basic strategy.

Basic strategy is the complete set of optimal plays for every possible combination of your hand against the dealer’s upcard. It was derived through probability analysis and computer simulation, not intuition or superstition. When played consistently and correctly, basic strategy reduces the house edge to approximately 0.5% in a standard six-deck game dealt under S17 rules (where the dealer stands on soft 17). That is one of the lowest house edges of any casino game.

This guide does not promise you will win every session. Variance is real, and short-term results can diverge significantly from the mathematical expectation. What basic strategy does is ensure that, over every hand you play, you are making the best available decision given the information on the table.

What is basic strategy?

Basic strategy is a decision matrix built from exhaustive probability analysis. For every possible player hand — factoring in the total value and whether the hand is hard, soft, or a pair — and for every possible dealer upcard from 2 through ace, the strategy calculates the expected value of each available action and prescribes the one with the highest expected return.

A hard hand is any hand that either contains no ace, or contains an ace that must be counted as 1 to avoid busting. A hard 16 made up of a 9 and a 7, for example, cannot be played with the ace counted as 11. A soft hand contains an ace that is currently counted as 11 without causing a bust — a soft 17 might be an ace and a 6. The distinction matters because soft hands carry more flexibility: you can take an additional card without the immediate risk of busting.

The mathematical foundation for basic strategy was formalised by Edward Thorp in his 1962 book Beat the Dealer, which used early computer analysis to calculate the optimal play for each hand combination. Subsequent research, including work by Julian Braun and others, refined the strategy for specific rule variations. The core decisions have remained stable for decades because the underlying probabilities do not change.

Basic strategy applies to single-deck through eight-deck games, though the correct plays shift slightly depending on the number of decks and the specific table rules in place. This guide covers the standard six-deck, S17 version, which is the most common configuration you will encounter.

How to read the strategy chart

A basic strategy chart organises every decision into a grid. The rows represent your hand — listed as hard totals (hard 5 through hard 21), soft totals (soft 13 through soft 21), and pairs (2-2 through A-A). The columns represent the dealer’s upcard, running from 2 through 10 and then ace.

Each cell in the grid contains an action code:

• H — Hit
• S — Stand
• D — Double down if the rules allow; otherwise hit
• Ds — Double down if the rules allow; otherwise stand
• P — Split
• P/H — Split if double after split (DAS) is allowed; otherwise hit

To use the chart, find the row matching your hand, find the column matching the dealer’s upcard, and take the prescribed action. There is no interpretation required. The chart is the answer.

Once you have memorised the chart, you will no longer need it at the table. Until then, many casinos permit players to consult a printed strategy card during play — using one is not cheating, and it is always worth checking the house rules before sitting down.

Hard hand strategy

Hard hands form the majority of decisions you will face. The logic behind each range of totals follows a coherent principle: when the dealer is weak (showing a low upcard), you play conservatively and let the dealer bust; when the dealer is strong, you take more risk because standing on a poor total is unlikely to win.

Hard 8 or less. Always hit. Your total is too low to have any realistic chance of busting on a single card, and standing would leave you with a value the dealer nearly always beats.

Hard 9. Double down against a dealer upcard of 3, 4, 5, or 6. These are the dealer’s weakest cards — a 4, 5, or 6 upcard means the dealer has a meaningful chance of busting, and doubling lets you maximise your return when you are the favourite. Against dealer 2 or 7 through ace, hit.

Hard 10. Double down against dealer 2 through 9. A starting total of 10 is strong enough that doubling is correct across a wide range of dealer upcards. The only exceptions are dealer 10 and dealer ace, where the dealer’s strength narrows the gap enough that hitting is preferred.

Hard 11. Double down against dealer 2 through 10. Hard 11 is the strongest doubling hand in the game — there are more 10-value cards in the deck than any other denomination, making a 21 the most likely single-card outcome. Against a dealer ace, hit rather than double; the dealer’s potential for blackjack or a strong hand tips the balance.

Hard 12. Stand against dealer 4, 5, or 6; hit against everything else. Hard 12 is an uncomfortable hand because there are four card values (10, J, Q, K) that bust you immediately, but the total is still too low to stand against a dealer showing a strong upcard. Against 4, 5, and 6, the dealer’s bust probability is high enough that standing and waiting is the correct play.

Hard 13 through 16. Stand against dealer 2 through 6; hit against dealer 7 through ace. This is the region where most players make expensive mistakes. Hard 16 in particular feels like a losing hand regardless of what you do — and over the long run it often is — but the math is clear: against a dealer 7 or higher, you must hit. Standing on 16 versus a dealer 7 is one of the most common and costly errors in recreational blackjack.

Hard 17 and above. Always stand. The risk of busting on any additional card outweighs the potential gain of improving the total.

Soft hand strategy

Soft hands are underutilised by many players because they look deceptively strong. An ace-7 giving you a soft 18 feels like a comfortable hand, and many players simply stand. But soft hands offer opportunities to double down that increase your expected return — particularly when the dealer is showing a weak upcard.

Soft 13 and 14 (A-2, A-3). Double against dealer 5 or 6, otherwise hit. These are modest totals with limited doubling value; the opportunity only arises when the dealer’s two weakest upcards are showing.

Soft 15 and 16 (A-4, A-5). Double against dealer 4, 5, or 6, otherwise hit. The range widens slightly as your total improves and you become more likely to finish with a competitive hand after doubling.

Soft 17 (A-6). Double against dealer 3 through 6, otherwise hit. Many players stand on soft 17 instinctively, but this is a mistake. A total of 17 does not win very often — the dealer makes 17 or better a high percentage of the time — and doubling against a weak dealer upcard is the correct mathematical response.

Soft 18 (A-7). This is the most nuanced soft hand. Double against dealer 3 through 6. Stand against dealer 2, 7, or 8. Hit against dealer 9, 10, or ace. Soft 18 looks like a strong hand, and against a dealer 7 or 8 it is — standing is correct. But against dealer 9, 10, or ace, the dealer is likely to make a better hand, and hitting (with the safety net of the flexible ace) is mathematically superior to standing and hoping for the best. Against the weakest dealer upcards, doubling extracts additional value.

Soft 19, 20, and 21. Always stand. These are strong totals with no meaningful case for any other action.

Pair splitting strategy

When you are dealt a pair, you have the option to split it into two separate hands by placing a second bet equal to your original wager. Some pairs should always be split; others should never be. The decision depends on the relative strength of your pair versus the dealer’s upcard, and in some cases on whether the house rules allow doubling after a split (DAS).

Always split aces. A pair of aces gives you a combined soft total of either 12 or 2 — neither is strong. Split them unconditionally. Each ace becomes the foundation of a new hand, and you are drawing to a 21 on each. Most casinos restrict players to one additional card per split ace, which still makes splitting the correct decision by a wide margin.

Always split 8s. A pair of 8s totals 16, which is the worst hand in blackjack — it is weak enough to lose to nearly every dealer total, yet high enough that hitting carries a significant bust risk. Split them against every dealer upcard, including 10 and ace. You will not win every resulting hand, but splitting 8s against a dealer 10 loses less money over time than playing a hard 16.

Never split 10s. A pair of 10-value cards gives you 20, which wins the majority of the time. Splitting breaks up one strong hand into two that will more often finish with 20 or less. The expected value of standing on 20 is significantly higher.

Never split 5s. A pair of 5s is a hard 10 — one of the best doubling hands in the game. Splitting 5s creates two starting totals of 5, which are significantly weaker.

Split 9s against dealer 2 through 6 and 8 through 9. Stand against dealer 7 (your 18 beats a likely dealer 17), 10, and ace.

Split 7s against dealer 2 through 7. Against higher upcards, hit.

Split 6s against dealer 2 through 6. With DAS allowed, extend this to dealer 7.

Split 4s only with DAS allowed, and only against dealer 5 or 6. In most other situations, treat a pair of 4s as a hard 8 and hit.

Split 2s and 3s against dealer 2 through 7. Against higher upcards, hit.

Common mistakes

Even players who have studied basic strategy make consistent errors under the pressure of live play. These are the most costly:

Taking insurance. Insurance is a side bet that the dealer has blackjack when showing an ace. The payout is 2:1, but the probability of the dealer having a 10-value hole card does not justify the bet in a multi-deck game. For a non-blackjack hand, taking insurance has a negative expected value and should be declined every time.

Standing on 16 vs dealer 7 out of fear. This is one of the most common departures from basic strategy. Hard 16 is a genuinely bad hand, but standing against a dealer 7 is worse than hitting. The dealer is likely to finish with 17 or more, and your only path to improving your position is to draw.

Not doubling 11 vs dealer 10. Some players hesitate to double their bet when the dealer shows a 10, reasoning that the dealer has a strong hand. The math does not support this caution. Hard 11 against a dealer 10 is still a doubling situation; your expected gain from doubling exceeds the expected gain from hitting.

Splitting 10s. The rationale — “I could win two hands instead of one” — ignores the fact that 20 is already an extremely strong hand. Splitting it is a mathematically poor decision regardless of what the dealer is showing.

Memorising the chart

Learning basic strategy fully takes time, but you do not need to master every cell at once. A practical approach: start with hard totals, which account for roughly 70% of all decisions. Once hard totals are automatic, move on to pair splitting rules, then finish with soft hand decisions.

Practice with free play rather than real money. Playing at your own pace, without the time pressure of a live table, makes it easier to check your decisions against the chart and build genuine recall. The blackjack practice game on this site lets you play at whatever speed you need.

For the full rules that inform when basic strategy decisions apply — including how doubling restrictions, surrender rules, and number of decks affect the correct play — see the complete blackjack rules guide.