You're dealt a pair of aces. The dealer shows a 4. Split or play it as one hand? Basic strategy answers:
| Split ← | +0.5660 |
| Hit | +0.1266 |
| Double | +0.0584 |
| Stand | -0.2111 |
| You bust on the next card | 0.0% |
| Dealer 4 busts | 39.4% |
Split is not close: it beats Hit by 0.4394 per unit. Getting this one wrong costs $4.39 on a $10 bet, every single time. Across the 340 situations in this chart it ranks 39th by expected value — better than 301 of them, worse than 38. 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.
Two aces are worth 12 together — a terrible total. Split, and each ace becomes the start of a hand worth ~52% of a blackjack. Splitting aces is the single most profitable move in the game, against any dealer card, including a 4.