Two pairs with one thing in common
Almost every chart agrees on a short list: split aces, split eights. They are the two pairs that are nearly always split regardless of the dealer’s upcard. At first glance the pairs are unrelated, since aces are the best starting card and eights make one of the worst totals. The common thread is that in both cases the combined hand is worse than two separate hands would be.
Why aces are split
Two aces together are a hard 12 (or a soft 12 when one is counted as 11), a weak hand that you would usually have to hit and sometimes bust. Apart, each ace is the strongest starting card in the game.
An ace as a first card is useful in several ways:
- It can become 21 with a single ten-valued card, a hand that is about 31 percent likely on each draw, because ten, jack, queen and king all count as ten.
- It can become a strong 18 to 20 with a 7, 8 or 9.
- It can never bust on the next card, as it is a soft hand.
So each of the two hands begins with an advantage that the combined 12 does not have. The cost is a second bet, but the extra bet goes on a hand that, on average, is clearly better than the one it replaces.
One caution: 21 reached after a split is normally paid as an ordinary win at 1 to 1, not as a natural at 3 to 2, at most tables. This lowers the value slightly, but the split remains correct.
Why eights are split
Eight plus eight is a hard 16. That is the same hand discussed in the piece on hard sixteen, a hand that loses more than it wins regardless of how you play it, especially against a 9, 10 or ace.
Splitting does not make eights a good starting card. It makes them a less bad one. A hand starting at 8 cannot be busted by a single hit, and a decent range of cards improve it: a 10 gives 18, a 9 gives 17, a 3 gives 11, which is a good doubling total. By comparison, a 16 can only be made worse by a large range of cards.
Here is a simple, illustrative way to see this. With a bet of 10 units, you can compare:
- Keep the 16 against a dealer 10. Standing or hitting both tend to lose more often than they win, and the loss on average is a good fraction of your bet.
- Split. You now have 20 units at risk across two hands that each begin from 8.
The point is not that you win. It is that the average loss across the two split hands is typically smaller than the loss on the unsplit 16, even though you have staked more. Splitting here is damage control, and that is also why a few charts, when surrender is available, prefer surrender for 8,8 against an ace in some rule sets.
Why dealer strength matters less here
Most pairs are split only against weak dealer cards. Aces and eights are different because their combined hands are bad enough that a strong dealer does not change the answer. Even against a 10 or ace, the unsplit alternative is worse. This is the key to the “always split” rule. The weak and strong dealer card groups still matter, as explained in the article on dealer bust cards, but they change the size of the benefit more than its direction.
Where table rules reduce the benefit
The rules around splitting can change how attractive the split is.
- One card on split aces. Many tables give you only one card on each ace and do not allow further hitting. This lowers the value of the split, but it generally remains correct.
- Resplitting. If you draw another ace or eight, some tables allow you to split again and some do not. Details vary, as summarised in the guide to resplit limits.
- Doubling after a split. Where allowed, it adds a little value to split eights, which can draw to 11.
- Dealer rules. Whether the dealer hits soft seventeen changes a few borderline cases, mainly involving surrender and eights against an ace.
Because these rules vary, it is worth reading the rules at the table before sitting down.
What this does not mean
Splitting aces and eights is a way to reduce losses and slightly improve results over many hands, not a guarantee. An ace split can easily end up as two weak hands, and a pair of eights can turn into two losses with double the money out. Every hand still carries the house edge, and previous hands never alter what comes next.
Only play with money you can afford to lose. If gambling stops being fun or starts to cause difficulty, contact a local support service.