You split a pair of aces. The dealer lays one card on each: a seven on the first, and on the second, another ace. Now what?
At some tables you may split again. At others you may not, and you are left holding two aces you cannot draw to, a soft 12 frozen in place. Which of those happens is printed on the felt in three letters most players never read, and it is a small but real piece of the arithmetic of the game.
What RSA actually means
RSA stands for resplit aces. It is the rule that decides whether a second ace on a split ace can be split again, usually up to a stated limit of three or four total hands.
It sits alongside a second rule that is near universal: one card only to each split ace. When you split aces, the dealer gives each ace exactly one card and the hand is finished, whatever it turns out to be. You cannot hit an ace and a four to try for better. That restriction exists because two hands each starting at eleven would otherwise be an enormous player advantage, and casinos have limited it since long before anyone published a strategy chart.
Put those two rules together and the shape of the problem is clear. One card only means a hand that lands on an ace has nowhere to go, so whether you can split it out is the only lever available.
Why aces are the hand where it matters most
Resplitting is available for other pairs too, and it matters much less for them. If you split eights and catch another eight, you can split it or you can simply play the 16 out, hitting as basic strategy tells you. The hand still has options.
A second ace on a split ace has no options at all. Ace plus ace counted as soft 12 with no draw allowed is close to a dead hand: it beats nothing except a dealer bust. If the table lets you split it, that near dead hand becomes a fresh hand starting at eleven, which is the best starting total in blackjack. The swing per occurrence is large.
Work through the arithmetic informally and it makes sense. A hand of ace plus ace with no draw is worth barely more than a hard 12 that has been frozen, since it wins only when the dealer breaks. Split it and you hold a hand that turns into 21 whenever a ten arrives, which is close to a third of the shoe, and into a strong nineteen or twenty when an eight or a nine arrives. Trading the first for the second is one of the largest single upgrades any table rule offers.
What keeps the overall figure modest is frequency. Being dealt a pair of aces and then catching a third is not common. A big improvement on a rare hand comes out as a small number in the long run average, which is exactly what the published tables show.
What the rule is worth
As Wizard of Odds calculates, measured against a baseline of eight decks with the dealer standing on soft 17 and doubling after a split allowed, allowing the player to resplit aces is worth about 0.08 percent. Positive figures favor the player.
For comparison, the same source puts the cost of not allowing any pair to be resplit, compared with a game permitting resplits to four hands, at about 0.06 percent. Both numbers live in the same modest range, and both are the sort of thing that gets ignored one at a time.
They should not be ignored together. RSA is the exception rather than the norm: plenty of games allow resplitting of ordinary pairs while stopping short at aces, so seeing the rule on the felt is a signal that the game is a little more liberal than average.
The small rules, side by side
Here is the wider set, all from the same source and the same baseline of eight decks, dealer stands on soft 17, double after split allowed. Positive means the rule favors the player.
| Rule | Effect on the player |
|---|---|
| Player may resplit aces | +0.08% |
| Late surrender offered | +0.08% |
| Four decks instead of eight | +0.06% |
| Double deck instead of eight | +0.19% |
| Single deck instead of eight | +0.48% |
| No resplitting of any pair (vs resplit to four hands) | about -0.06% |
| No doubling after a split | -0.14% |
| Dealer hits soft 17 | -0.22% |
| Blackjack pays 6:5 | -1.39% |
| Blackjack pays 1:1 | -2.27% |
Two things jump out of that list. The first is how tightly clustered the rule variations are: almost everything except the payout and the deck count lives between 0.06 and 0.22 percent. The second is how completely the payout line dominates. A 6:5 game at about 1.39 percentage points against you outweighs every other row combined, several times over, which is why our guide to 3:2 versus 6:5 treats it as the first thing to check and everything else as detail.
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Rules stack, so read the felt
Rule effects like these combine additively, closely enough for practical purposes, and that is exactly how published tables are meant to be used. Take a baseline house edge for the game in front of you, then add and subtract each difference you can see.
Worked through, that turns an abstract list into a habit. Two tables in the same room can differ by a quarter of a percentage point on rules alone, before anyone deals a card, and the difference is written on the layout: number of decks, whether the dealer hits soft 17, whether doubling after a split is permitted, whether surrender is offered, whether aces may be resplit, and above all what a blackjack pays.
Comparing two games is arithmetic, not intuition, and it is what our house edge rule calculator guide is about. The app carries the same idea: nine casino presets and full rule customization, with charts that redraw automatically when you change the rules, so you can see both the edge and the strategy move together.
Where the rules change your play
Rules do not only move the edge. Some of them move the correct decision, which is why memorizing one chart and carrying it everywhere is a quiet leak. Doubling after a split changes several pair decisions, because a pair is worth splitting more often when the resulting hands can be doubled. A dealer who hits soft 17 shifts a handful of plays as well, covered in our comparison of S17 and H17.
Resplitting aces is gentler on this front. Whether or not the table allows it, the correct play with a pair of aces is the same: split them. Always split aces is one of the few decisions in blackjack that holds under essentially every rule set, and it is one of the first things a player should learn about splitting pairs. RSA changes what happens afterwards, not what you do at the moment of decision.
That is worth keeping in perspective. Finding a table with resplit aces is a modest improvement on the margins of a game where correct play still leaves the house with a small edge, and where a single session's result is dominated by variance rather than by any rule on this page. Reading the felt is free, and it is worth doing. It is not a strategy for winning, and nothing here promises one.
Frequently asked questions
What does resplitting aces mean in blackjack?
You split a pair of aces, the dealer places one card on each ace, and if one of those cards is another ace the table either lets you split again or does not. Tables that allow it are described as offering RSA, resplit aces. Where it is not allowed you are stuck holding a soft 12 that you cannot draw to, which is close to a dead hand.
How much is resplitting aces worth to the player?
As Wizard of Odds calculates, against a baseline of eight decks with the dealer standing on soft 17 and doubling after a split allowed, permitting resplit aces is worth about 0.08 percent to the player. That is a small number on its own, comparable to the value of late surrender, and it matters mainly as one of several small rules that add together.
Why do you only get one card on each split ace?
It is a house restriction, and it is close to universal. Two aces split into two hands each starting at eleven, which is the strongest starting point in the game, so casinos limit the draw to a single card to hold back the player advantage. Splitting aces is still correct basic strategy under essentially all rule sets, one card limit included.
What does it cost if a table does not allow resplitting any pair?
As Wizard of Odds calculates, not allowing any pair to be resplit costs about 0.06 percent compared with a game that permits resplitting to four hands. Like most split rules it is a small figure taken alone. Its significance is that it stacks with the other rule differences on the felt, and several small negatives together stop being small.
Do blackjack table rules add together?
Yes, they combine additively closely enough for practical purposes, which is how published rule effect tables are meant to be used. Start from a baseline house edge for a given game, then add and subtract each rule difference. A 6:5 payout at about 1.39 percentage points against you will dominate every other line in the sum, so check the payout first.