You hold Ace-7 — a soft 18, meaning the ace still counts as 11. Dealer shows 4. The correct basic-strategy play:
| Double ← | +0.2370 |
| Stand | +0.1759 |
| Hit | +0.1185 |
| You bust on the next card | 0.0% |
| Dealer 4 busts | 39.4% |
Double is worth 0.0612 more per unit than Stand. On a $10 bet that is $0.61 handed over every time you get it wrong. Across the 340 situations in this chart it ranks 91st by expected value — better than 249 of them, worse than 90. Expected value is per unit staked, computed for multi-deck, dealer stands on soft 17, double after split allowed. The model and the code are published as data.
Against a weak dealer 4 (40% bust chance), soft 18 (Ace-7) is a doubling machine: you can't bust the draw, and every extra chip is placed while the dealer is in trouble. Double — if the table does not allow it, stand on your 18.
Soft hands are where most casual players leak the most: they play them like hard totals and miss every profitable double. Learning the six soft-total rows of the chart is the fastest win-rate upgrade there is.