Splitting is the most misplayed decision in blackjack. Get it right and you turn weak hands into two strong ones; get it wrong and you double your money on a losing spot. Here's exactly when to split pairs in blackjack, pair by pair, for a standard multi-deck game.
The Two You Always Split: Aces and 8s
Always split Aces. Two aces played as one hand is a soft 12 — mediocre. Split them and each ace starts a new hand with a great shot at 21 (note: most casinos deal only one card to each split ace).
Always split 8s. A pair of 8s is a hard 16 — statistically the worst total in the game. Splitting gives you two hands starting with 8, each of which can grow into 18, 19 or 20. Even against a dealer 9, 10 or Ace, splitting loses less over time than standing on 16.
The Two You Never Split: 10s and 5s
Never split 10-value cards. Two tens is a made 20 — one of the strongest hands possible. Breaking it up to chase two 20s is greedy and mathematically worse. Keep the 20 and stand.
Never split 5s. A pair of 5s is a hard 10 — a doubling hand. Splitting into two hands each starting with a 5 is far weaker than doubling or hitting the 10.
The Conditional Pairs
The rest depend on the dealer's upcard, because splitting only pays when the dealer is in a weak spot (showing a low card likely to bust).
9s: Split against 2–6 and against 8 or 9. Stand against 7, 10 or Ace. The exception at 7 looks odd, but two 9s make 18, and against a dealer 7 the dealer most often ends on 17 — so your 18 already wins; don't risk it.
7s: Split against 2 through 7. Otherwise hit.
6s: Split against 2 through 6 (against a 2, only if doubling after split is allowed). Otherwise hit.
2s and 3s: Split against 4 through 7 (and against 2–3 if double-after-split is allowed). Otherwise hit.
4s: Only split against a dealer 5 or 6, and only if doubling after split is allowed. Otherwise just hit.
Why "Double After Split" Matters
Several of these calls flip based on one table rule: DAS (double after split). When you're allowed to double on a hand you've just split into, splitting becomes more valuable, so a few borderline pairs (2s, 3s, 4s, 6s) become splits. Check the felt or ask the dealer.
Drill It Until It's Automatic
Nobody memorizes ten pair rules by reading them once. Load the trainer's Pairs mode and run through random pairs against random upcards until the right answer is instant — that's when it starts saving you money at a real table.
Put this into practice — drill the exact basic-strategy chart against every dealer upcard.
Open the Free Trainer →