When to Split Pairs in Blackjack
Updated
Always split aces and eights. Never split tens or fives. Every other pair depends on what the dealer is showing: twos, threes, sixes, and sevens go against a weak upcard, and nines go against almost everything except a 7, a ten, and an ace. Whether the house allows doubling after a split moves a few of these.
- A,A and 8,8: always split.
- 10,10 and 5,5: never split.
- Everything else follows the dealer's upcard.
- DAS (double after split) adds a few splits against low cards.
The split chart
| Pair | Split against |
|---|---|
| A,A | Everything |
| 8,8 | Everything |
| 9,9 | 2 through 6, plus 8 and 9. Stand against 7, 10, and A |
| 7,7 | 2 through 7 |
| 6,6 | 2 through 6 |
| 3,3 and 2,2 | 2 through 7 |
| 4,4 | 5 and 6 only, and only with DAS |
| 5,5 and 10,10 | Never |
Six decks, dealer stands on soft 17, double after split allowed. Without DAS, the 4,4 split disappears and 2,2 and 3,3 stop being splits against a dealer 2 and 3. The chart generator builds the exact version for your table.
Why aces and eights always split
These two are the famous ones, and the reasoning is different for each.
Two aces played as one hand total 12, because only one of them can be worth 11. That is a mediocre hand that cannot even be improved much. Split them and each hand starts on 11, the strongest opening position in the game. It is such a large gain that you split aces against a dealer ace.
Two eights total 16, the single worst hand in blackjack. Split them and you own two hands starting on 8, which is not great but is enormously better than one hand you expect to lose. You are not splitting to win here, you are splitting to lose less, and against a ten it is still correct by a clear margin.
Why tens and fives never split
10,10 is a 20. It wins the great majority of the time exactly as it stands. Splitting trades one near-certain winner for two ordinary hands, and it loses money even against a dealer 5 or 6, where the temptation is strongest. Card counters do deviate here at extreme true counts, but that is a different game with different information.
5,5 is a 10. Play it as a 10 and double it against anything from 2 through 9. Splitting turns your best doubling hand into two hands starting on 5, which is close to the worst start available.
If you take away one habit from this page, make it these two. They are the most expensive splitting mistakes people make, because they feel clever.
The 9,9 puzzle
This is the pair that trips up otherwise solid players. You split nines against 2 through 6, and also against 8 and 9, but you stand against a 7.
The logic is that a dealer showing 7 makes 17 more often than any other total, about 37% of the time. Your 18 already beats that. Splitting risks a hand that is winning to chase two hands that might not be, so you take the 18 and move on.
Against a 10 or an ace you stand for a different reason: those upcards are strong enough that two fresh nines will not fix anything, and 18 at least has a pulse.
What double after split changes
DAS means you can double on a hand created by a split. It is worth about 0.14% to you, and it makes several marginal splits worthwhile that otherwise are not.
With DAS you gain the 4,4 split against 5 and 6, and you gain 2,2 and 3,3 against a dealer 2 and 3. The reasoning is the same each time: splitting into low cards often produces a 9, 10, or 11, and being able to double those is what tips the balance.
Without DAS, play those cells as plain hands and do not split.
Deviations at a high count
Card counters change a handful of splits when the true count runs high. The best known is splitting 10,10 against a 5 or a 6 at a high count, which is correct math and also a good way to get a floor supervisor's attention.
Our live counter shows these in progressive mode, along with the true count each one turns on at.
• Aces and eights, every time.
• Tens and fives, never.
• Small pairs go against small upcards.
• Nines stand against 7, 10, and ace.
• DAS adds a few splits against low cards.
How many times can you split?
Typically up to four hands, meaning three splits, though the placard is the authority. Aces are usually limited to a single split with one card each, and some houses do allow resplitting aces, which is worth about 0.08% to you.
Every split costs another full bet, so a hand that started at $25 can be $100 on the felt before the dealer turns a card. That is worth knowing before you sit down at a limit that is already stretching your bankroll.
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By Martin Kosek · every number on this site is computed by us, not copied.
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