You're dealt a pair of 9s. The dealer shows a 5. Split or play it as one hand? Basic strategy answers:
| Split ← | +0.3634 |
| Stand | +0.1996 |
| Hit | -0.6153 |
| Double | -1.2305 |
| You bust on the next card | 76.9% |
| Dealer 5 busts | 41.6% |
Split is not close: it beats Stand by 0.1638 per unit. Getting this one wrong costs $1.64 on a $10 bet, every single time. Across the 340 situations in this chart it ranks 72nd by expected value — better than 268 of them, worse than 71. 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 dealer 5 (42% bust chance), splitting 9s turns one mediocre total into two playable hands while the dealer is vulnerable. With double-after-split allowed, you also keep the option to press each new hand — that's where the split profit comes from.
Note the famous 9-9 exception: against a 7 you stand, because your 18 beats the dealer's likely 17. Against 8 or 9 you split again. It's the trickiest row of the whole chart.