Blackjack is routinely described as the casino game with the lowest house edge. That is true — but only for a player who makes the mathematically correct decision every time. The complete set of those decisions is known as basic strategy, and it has been worked out by computer simulation of every possible hand against every possible dealer card. This guide explains what basic strategy is, roughly what it says, what it achieves, and — just as importantly — what it does not.
The idea
In blackjack, the player makes decisions: hit, stand, double down, split, or (where offered) surrender. For every combination of your hand and the dealer’s up-card, one of those choices produces the highest expected return. Basic strategy is simply the table of those best choices. It assumes no knowledge of cards already dealt — it is purely about the current hand and the visible dealer card.
The strategy varies slightly with the rules of the specific game (number of decks, whether the dealer hits soft 17, whether you can double after splitting), but the core decisions are stable.
The main rules in summary
Hard totals (no ace, or an ace counted as 1):
| Your total | Dealer 2–6 | Dealer 7–A |
| 8 or less | Hit | Hit |
| 9 | Double vs 3–6, else hit | Hit |
| 10 | Double | Double vs 7–9, hit vs 10/A |
| 11 | Double | Double (hit vs A in some rules) |
| 12 | Stand vs 4–6, hit vs 2–3 | Hit |
| 13–16 | Stand | Hit |
| 17+ | Stand | Stand |
Soft totals (an ace counted as 11):
| Your hand | Guidance |
| Soft 13–14 (A-2, A-3) | Double vs 5–6, else hit |
| Soft 15–16 (A-4, A-5) | Double vs 4–6, else hit |
| Soft 17 (A-6) | Double vs 3–6, else hit |
| Soft 18 (A-7) | Double vs 3–6; stand vs 2, 7, 8; hit vs 9, 10, A |
| Soft 19+ | Stand |
Pairs:
| Pair | Guidance |
| A-A, 8-8 | Always split |
| 10-10, 5-5 | Never split (treat 5-5 as hard 10) |
| 9-9 | Split vs 2–9 except 7; stand vs 7, 10, A |
| 7-7 | Split vs 2–7 |
| 6-6 | Split vs 2–6 |
| 4-4 | Split vs 5–6 only (if double after split allowed) |
| 3-3, 2-2 | Split vs 2–7 |
Full charts for specific rule sets are freely available, and there is no rule against consulting one while playing online.
What it achieves
Under typical rules — six decks, dealer stands on soft 17, blackjack pays 3:2, doubling allowed after a split — perfect basic strategy reduces the house edge to roughly 0.5%. A player making intuitive decisions (“stand on 16 because I’ll bust”, “never split”) typically gives the house 2% or more. Over £1,000 of play, that is the difference between an expected loss of £5 and £20 or more.
What it does not achieve
Basic strategy minimises the house edge. It does not eliminate it, and it does not give the player an advantage. Over the long run, a perfect basic strategy player still loses about half a percent of everything they wager.
Card counting is the technique that can, in theory, shift the edge to the player. It works by tracking the ratio of high to low cards remaining in the shoe and raising bets when the remaining cards favour the player. It is impractical online: RNG blackjack effectively reshuffles every hand, and live dealer games use frequent shuffles and cut cards specifically to limit its value.
Rule variations and their cost
The house edge moves with the rules. The most important ones:
| Rule | Effect on house edge |
| Blackjack pays 6:5 instead of 3:2 | +1.4% (avoid these games) |
| Dealer hits soft 17 | +0.2% |
| Single deck instead of six | −0.5% |
| No doubling after split | +0.1% |
| Doubling only on 10 or 11 | +0.2% |
| Surrender allowed | −0.1% |
| Dealer does not peek for blackjack (European) | +0.1% |
The 6:5 payout is the single most damaging variation and is increasingly common. Always check what a natural blackjack pays before sitting down.
Side bets
Perfect Pairs, 21+3, insurance and similar side bets carry house edges of 3% to 10% or more. Insurance in particular is a bet that the dealer has a ten under an ace; it pays 2:1 but the true odds are worse than that, and basic strategy says never to take it.
Practical takeaways
- Learn the pairs and soft-total rules first; they are where intuition is most often wrong.
- Never play a 6:5 game if a 3:2 game is available.
- Ignore side bets.
- Understand that even perfect play is a slow, small expected loss, not a route to profit.
Related reading on site: Casino Guide; “Luck vs. Strategy: How Much Skill Can You Use in Casino Games?”
Even with perfect play, the casino retains an edge. Set a budget before you begin.
