Blackjack Basic Strategy: The Complete Decision Guide

Basic strategy is the mathematically optimal decision for every blackjack hand against every dealer upcard. Play it perfectly and the house edge drops to roughly 0.5% in a standard 6-deck game — the lowest of any casino table game.

What Basic Strategy Is

Basic strategy is a complete lookup table: for every possible combination of your hand total and the dealer's upcard, it tells you the single action that maximizes expected value — hit, stand, double, split, or surrender. There are no probabilities to track, no card counting required. It is purely a function of your cards and the one dealer card you can see.

The strategy was first published by Roger Baldwin, Wilbert Cantey, Herbert Maisel, and James McDermott in 1956, derived by hand calculation on adding machines. Edward Thorp refined and popularized it in Beat the Dealer (1962). Modern computer simulation has confirmed every entry across billions of hands. The chart is settled mathematics — there is nothing left to argue about.

What It Gives You

Against a typical 6-deck, dealer-stands-soft-17 (S17) game, perfect basic strategy reduces the house edge to approximately 0.43%. In a dealer-hits-soft-17 (H17) game — now standard on most Las Vegas Strip shoe tables — the house edge rises to about 0.65%. Either way, it is far lower than the 2–5% most casual players give up by guessing.

Basic strategy is also the foundation for card counting. No counting system makes sense without first mastering the baseline decisions — deviations are only valuable when you know what you're deviating from.

Hard Totals

A hard hand is any hand without an ace, or any hand where the ace can only count as 1. Hard hands are the most common situation you'll face.

The hard 12–16 zone is where most players hemorrhage money. The instinct is to stand on stiff hands to avoid busting — but vs dealer 7 through Ace, the dealer will make 17 or better over 75% of the time. Hitting a hard 16 vs a dealer 10 loses less in the long run than standing, even though hitting feels terrible. The math doesn't care about feelings.

Soft Totals

A soft hand contains an ace counted as 11. Soft hands give you insurance against busting — if the next card would push you over 21, the ace drops to 1. That asymmetry makes soft hands significantly more aggressive to play than their totals suggest.

Soft 18 is the most misplayed soft hand at the table. Many players always stand, reasoning that 18 is a strong total. Against a dealer 9, 10, or Ace, standing with soft 18 is a losing play — the dealer's likely upcard distribution makes hitting (or doubling where allowed) the higher-EV choice.

Pairs

When you're dealt a pair, basic strategy considers whether splitting into two separate hands produces better expected value than playing the pair total. The answer is highly card-dependent — a pair of 8s is always split (hard 16 is the worst hand in blackjack); a pair of 5s is never split (hard 10 is excellent).

Surrender

Late surrender — available in many shoe games — lets you forfeit half your bet before drawing when the dealer's upcard makes your position nearly hopeless. The correct surrenders in a 6-deck H17 game are:

• Hard 16 vs dealer 9, 10, Ace (except pair of 8s vs Ace — split instead)
• Hard 15 vs dealer 10
• Hard 15 vs dealer Ace (H17 games only)

If a casino does not offer surrender, skip these exceptions and apply the standard hit/stand rules.

Rule Variations That Change the Chart

Basic strategy is not universal — it shifts depending on the rules of the specific game you're playing. The biggest sources of change:

• Number of decks: Single-deck strategy differs from 6-deck in about a dozen spots. The full interactive chart at learn.21simulator.com/strategy/chart covers standard 6-deck rules.
• H17 vs S17: When the dealer hits soft 17, you should double down on soft 18 vs Ace (instead of hit) and make a few other adjustments. See the full H17 vs S17 comparison.
• DAS (double-after-split): When allowed, some marginal pairs become splits. Pairs of 2s and 3s are split against a dealer 2 only when DAS is available.
• No hole card (ENHC): In European games where the dealer takes a second card only after players act, a few doubling situations become hits to avoid doubled losses against a dealer blackjack.

Common Mistakes and What They Cost

Five deviations account for most of the EV leak among players who "mostly know basic strategy":

• Standing on hard 16 vs dealer 7: Costs roughly 4% EV vs the correct play (hit). Intuition says stand; math says hit.
• Not splitting 8s vs dealer 10: Splitting costs money on average — but standing on hard 16 costs more. Split the 8s.
• Standing on soft 18 vs dealer 9: Costs roughly 1.8% EV. Hit (or double vs 3–6).
• Not doubling 11 vs dealer 10: Gives up a high-positive-EV spot. Always double.
• Never surrendering: In games with late surrender, failing to surrender hard 16 vs dealer 10 costs about 2.9% EV on those specific hands.

How to Memorize the Chart

The full strategy chart has roughly 270 unique cells, but the underlying logic reduces to a much smaller set of rules. A practical learning sequence:

1. Hard totals — the largest category and the most frequently played. Learn the breakpoints: 8 and under always hit; 12–16 stand vs 2–6, hit vs 7–Ace; 17+ always stand.
2. Pairs — two absolute rules (always split 8s and aces; never split 5s and 10s) cover 80% of the EV. Learn the rest once you have the absolutes.
3. Soft totals — start with the high soft hands (18+) that are most commonly played wrong. Work down to the aggressive doubles.
4. Surrender — only 3–4 situations; memorize them last.

The strategy chart on this site links every cell to a detailed explanation with EV comparisons. Use it to review the hands you're unsure about. Running 10,000-hand simulations in 21simulator.com with "track decisions" enabled is the most efficient way to find your actual leak points.