You're dealt a pair of 5s. The dealer shows a 4. Split or play it as one hand? Basic strategy answers:
| Double ← | +0.4609 |
| Hit | +0.2305 |
| Split | -0.0330 |
| Stand | -0.2111 |
| You bust on the next card | 0.0% |
| Dealer 4 busts | 39.4% |
Double is not close: it beats Hit by 0.2305 per unit. Getting this one wrong costs $2.30 on a $10 bet, every single time. Across the 340 situations in this chart it ranks 54th by expected value — better than 286 of them, worse than 53. 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.
A pair of 5s is really a hard 10 — one of the best doubling totals in the game. Splitting would create two hands starting from 5, the worst possible start. Against a 4, play it as 10: double down and press your edge.