Hard 12 against a dealer 4
This is one of the closest decisions in blackjack. Stand is correct, but it beats hit by 0.24% of your bet — and of the 350 hand-versus-upcard spots on the chart, only 3 are closer.
Worth being blunt about what that expected return means: at -21.1%, you lose money on this hand in the long run whatever you do. Playing it correctly does not make it a good spot — it makes it a 0.24% less bad one. The choice is between two losing options, which is exactly why it gets argued about.
Every option, ranked
| Action | Expected return | Cost vs. best |
|---|---|---|
| Standcorrect | -21.11% | — |
| Hit | -21.35% | −0.24% |
| Double | -42.71% | −21.60% |
Expected return per unit staked, from an exact recursive engine rather than a copied chart. Figures are for Dealer Stands on Soft 17, DAS, pays 3:2. Actions not shown are not legal here.
The house rules do not change it
For all the argument this hand attracts, the answer is stable: every one of the 6 rule sets modelled gives the same correct play. What changes is how much it costs you, not what to do.
| S17 · 3:2 | Stand | -21.1% |
| H17 · 3:2 | Stand | -20.6% |
| S17 · Surrender | Stand | -21.1% |
| S17 · No DAS | Stand | -21.1% |
| S17 · No Peek | Stand | -21.1% |
| S17 · 6:5 | Stand | -21.1% |
Why it is close
Taking a card on hard 12 busts you 30.77% of the time. Standing hands the hand to a dealer showing 4, who — having already checked and not got blackjack — busts 39.4% of the time. Two bad numbers close together is the whole story — the decision is a choice between them, and neither rescues the hand. The bust odds page has both curves in full.
What the count does to this
Stand is correct at a neutral shoe, but not at every shoe. The two actions are worth exactly the same at a Hi-Lo true count of −0.36, so past that point hit is the better play — a deviation conventionally written as an index of 0.
This one is on Schlesinger’s Illustrious 18, the deviations that return the most to a counter, where it carries an index of 0 — the same number this engine arrives at independently.
Where that number comes from, and what one card of each rank is actually worth, is on the card counting page.