Why split 8s against a 10 if both hands are likely to lose?
Because a single hand of 16 against a 10 loses even more. Splitting reduces the expected loss from about 54 cents per dollar to roughly 48 cents, counting both bets.
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Blackjack Splitting Rules: When To Split Pairs
Updated
Splitting lets you turn a pair into two separate hands by matching your original bet. It is the right play when one weak hand becomes two decent ones (8,8 against anything) or when the dealer is weak enough that two bets are better than one (2,2 against a 6). It is wrong when you would be breaking up a strong hand (10,10) or when the dealer is too strong to justify doubling your exposure.
This guide assumes the trainer's rules: four decks, dealer stands on soft 17, and you may double after splitting (DAS). Without DAS, a few of the borderline splits against weak dealers become hits.
The absolute splits: aces and 8s
Split aces against every upcard. Two aces are a soft 12, which is a poor hand, but each ace alone is the best possible starting card. Most casinos deal only one card to each split ace; even so, splitting is strongly positive.
Split 8s against every upcard too, including the 10 and ace. A pair of 8s is hard 16, the worst total in the game. Two hands starting with 8 are each expected to lose less than one hand of 16, so you are spending a second bet to reduce your total loss. It does not feel like a winning play, and against a 10 it is not, but it loses less than standing or hitting 16.
The absolute non-splits: 10s and 5s
Never split 10s. A hard 20 wins about 85 percent of the time against any upcard, and two hands starting with 10 are each worse than that. Splitting 10s against a 6 is a frequent sight at casino tables and it costs money every time.
Never split 5s. Two 5s are a hard 10, which is a strong doubling hand against 2 through 9. Splitting them creates two hands starting with the worst possible card. Treat 5,5 exactly as you would treat 6,4 or 7,3.
The dealer-dependent splits
Split 9s against 2 to 6, 8 and 9. Against a 7 you stand, because the dealer's most likely finish is 17 and your 18 beats it. Against a 10 or ace you stand because splitting into two 9s against a strong card is worse than keeping 18.
Split 2s, 3s and 7s against 2 to 7, and 6s against 2 to 6. These are low pairs that make bad hard totals (4, 6, 12, 14) but become reasonable starting cards against a dealer who is likely to bust. Against 8 or higher you hit them as hard totals. Split 4s only against a 5 or 6; everywhere else, 4,4 is a hard 8 and you hit it.
Playing the hands after a split
Each split hand is played as a fresh two-card hand with the normal chart. If you split 8s and draw a 3 on the first hand you have hard 11: double it, since doubling after split is allowed here. If you draw another 8 you may usually re-split, and you should.
Watch the total exposure. A split followed by two doubles puts four bets on the table, which is correct play but needs a bankroll that can absorb losing all four. The bankroll guide covers sizing your base bet so the right split is never unaffordable.
Pair Splitting Chart (4 Decks, S17, DAS)
| Pair | Split Against | Otherwise | Reason |
|---|---|---|---|
| A,A | Everything | n/a | Each ace is the best starting card. |
| 10,10 | Never | Stand | 20 already wins about 85% of hands. |
| 9,9 | 2-6, 8, 9 | Stand | Keep 18 against a 7 (dealer likely 17) and against 10 or ace. |
| 8,8 | Everything | n/a | Two 8s lose less than one 16. |
| 7,7 | 2-7 | Hit | Hard 14 is weak; two 7s beat a bust-prone dealer. |
| 6,6 | 2-6 | Hit | Hard 12 versus a weak dealer becomes two playable hands. |
| 5,5 | Never | Double 2-9, hit 10-A | Treat as hard 10. |
| 4,4 | 5, 6 | Hit | Only worth it against the two weakest upcards. |
| 2,2 and 3,3 | 2-7 | Hit | Low pairs become fair hands against a weak dealer. |
FAQ
What does DAS mean and why does it matter?
DAS is double after split. When you may double the new hands formed by a split, borderline splits like 2,2 and 3,3 against a 2 or 3, and 4,4 against 5 or 6, become correct. Without DAS you hit those instead.
Can I re-split if I draw another matching card?
Most tables allow up to three or four hands. If re-splitting is allowed, re-split whenever the chart says to split that pair. Re-splitting aces is often not allowed.
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