Pairs: when two hands beat one

Splitting turns one hand into two, each with a full bet, so a split says the matchup is worth doubling your money in. There are two reasons that can be true. Your pair is a weak total but two strong starting cards, or the dealer is weak enough that you want more money on the table by any legal means.

Four pairs have no exceptions. Always split aces. Soft 12 is a poor total, and two hands that each start with an ace are the two best starts in the game, even where the casino gives split aces one card each. Always split 8s. Hard 16 is the worst hand in blackjack, and two hands starting from 8 are only mediocre. The split is an escape, and it is right even against a 10. Never split 10s. You would be breaking a made 20, which wins over 80% of the time, to chase two good-not-great hands. It is the most expensive aggressive play available. Never split 5s. Two 5s are a hard 10, so double.

The rest split into dealer weakness. 2s, 3s, and 7s split against 2–7. Two small hands are only worth funding when dealer busts pay for them. 6s split against 2–6. 4s split only against 5 and 6, and only when double-after-split is allowed, because two hands starting from a 4 are bad enough that you need both the weakest dealers and the option to double into them. 9s take the most thought. Split against 2–6 and against 8–9, and stand against 7. Your 18 beats the 17 a 7 usually makes, so leave it alone. Against 10 and ace, 18 is losing anyway. Stand and take your chances rather than fund a second losing hand.

Double-after-split (DAS) is what makes several of these splits profitable, so check for it at any real table. The Checkpoints here run with DAS on. The rule-variations Lesson covers what changes without it.