Splitting Pairs in Blackjack: The Rules
Last reviewed: June 2026
Split aces and 8s every time, never split 10s or 5s, and let the dealer’s upcard guide every other pair. Splitting is one of the highest-leverage decisions in blackjack — done correctly it can recover close to half a percent of expected value that most recreational players leave on the table.
What splitting does
When your first two cards are a matching pair, the casino lets you split them into two separate hands, each backed by an additional bet equal to your original wager. You then play each hand independently to completion. The strategic question is simple: are two independent hands starting from a single card worth more than the combined two-card total you already hold? Sometimes the answer is obviously yes (a pair of 8s is a terrible 16), sometimes obviously no (a pair of 10s is a near-perfect 20), and sometimes it depends on what the dealer is showing.
The complete split chart
| Pair | Always / Never | Dealer 2–6 | Dealer 7–A | Summary |
|---|---|---|---|---|
| A/A | Always | SPLIT | SPLIT | Two aces is a soft 12 — worst playable hand; convert to two chances at 21 |
| 8/8 | Always | SPLIT | SPLIT | 16 is the worst hard total; each 8 starts a new hand with real upside |
| 2/2 | Conditional | SPLIT (3–7) | Hit | Split when dealer is weak; hit against strong upcards |
| 3/3 | Conditional | SPLIT (4–7) | Hit | Narrow split range; dealer 2–3 is borderline, hit there |
| 4/4 | Conditional | SPLIT (5–6 only) | Hit | Only split against the two weakest dealer upcards |
| 5/5 | Never | DOUBLE | DOUBLE | 10 is a powerful doubling hand; splitting into two 5s throws that away |
| 6/6 | Conditional | SPLIT (2–6) | Hit | Split against full weak range; 12 on its own is unplayable |
| 7/7 | Conditional | SPLIT (2–7) | Hit | 14 is below par; split includes dealer 7 since ties push rather than win |
| 9/9 | Conditional | SPLIT (2–9, not 7) | Stand | 18 beats dealer 2–6 and 8–9; stand on 7 (your 18 already wins most) |
| 10/10 | Never | STAND | STAND | 20 wins roughly 97% of the time — never sacrifice it |
Why aces are always split
A pair of aces counts as soft 12 (one ace at 11, one at 1). That is mathematically the weakest hand you can hold — you are essentially starting from 2, because taking the higher value puts you at 12, a stiff total. When you split, each ace becomes the foundation of a brand-new hand. Draw a 10-value card on either one and you have 21; draw anything from 2 through 9 and you have a flexible soft total that cannot bust on the next card. The expected gain from splitting aces versus playing the soft 12 is among the largest of any split decision in the game.
Most casinos restrict split aces to one additional card per hand — you do not get to hit again if the result is unfavorable. That restriction is already priced into the strategy: split aces regardless.
Why 8s are always split
16 is the worst hard total in blackjack. You bust if you draw any card worth 7 or more (a roughly 54% chance), yet standing on 16 means the dealer only needs to make 17 or better to beat you — which happens far more often than not when the dealer shows a strong upcard. Either path is bad.
Splitting breaks the 16 into two hands each starting at 8, which is a neutral, flexible total. Draw a 2 through 3 and you have a soft or hard 10–11 that invites doubling. Draw a 10 and you have 18, which beats the dealer outright more than half the time. The math consistently shows that splitting 8s, even against a dealer 9, 10, or ace, produces a better expected outcome than playing the 16 as-is. Yes, you are putting more money at risk — but you are doing so from a position of strength rather than desperation.
Why 10s and 5s are never split
A pair of 10s totals 20. That hand wins against everything the dealer can make except a dealer 20 (a push) or 21 (a loss). Converting a 20 into two hands each starting at 10 is giving up near-certainty for two uncertain outcomes. The only way to break even on the split is if both resulting hands end up as 20 or 21 — a low-probability parlay. Stand on 20 every time.
A pair of 5s totals 10, which is one of the best doubling hands in the game. Doubling on 10 against a dealer showing 2 through 9 generates a significant expected value advantage — you draw exactly one card to a total of 10, which frequently produces 18, 19, or 20. Splitting into two hands starting at 5 wastes the power of the combined 10 and leaves you managing two weak starting points.
Conditional pairs: reading the dealer upcard
For pairs of 2s, 3s, 4s, 6s, 7s, and 9s, the dealer’s upcard is the deciding factor. The underlying logic is always the same: dealer upcards of 2 through 6 produce bust rates between roughly 35% and 42%. When the dealer is likely to bust, splitting low pairs to create two bets both positioned to win passively makes sense. When the dealer shows 7 through ace, the bust rate drops to roughly 15% to 25%, and your split hands start at a disadvantage — hitting (or standing) is often the better play.
The 9/9 case is slightly different. An 18 already beats many dealer totals, but it loses to dealer 9, 10, and ace. Splitting 9s against those strong upcards produces two hands that are likely to underperform — so you stand on the existing 18. Against a dealer 7, your 18 already beats the dealer’s most likely final total of 17, so there is no reason to break it up. Against 8 or 9, splitting gives each new hand a chance to improve beyond 18.
Resplitting and doubling after splitting
If you split a pair and then draw a third matching card, many casinos allow a resplit — splitting again to create a third hand. Rules vary widely, so check before you sit down. Resplitting aces is less commonly allowed than resplitting other pairs, but if permitted it is always correct to resplit.
Double after split (DAS) is another rule variant. If the casino allows it, you can double down on a hand created by a split — useful, for example, when you split 4s and draw a 7 to give yourself 11. This rule slightly shifts a few conditional split decisions in favor of splitting more aggressively; the chart above assumes DAS is available, which it is at most multi-deck games.
Both rules are addressed in detail in the blackjack basic strategy math breakdown.
How splitting fits into overall basic strategy
Splitting pairs is one component of a complete basic strategy system that also covers when to hit, stand, double, and surrender. Mastering splits alone will not eliminate the house edge, but combined with correct hitting and doubling decisions the full strategy reduces the house edge to approximately 0.5% on a standard 3:2 table. That is the lowest edge available to any casino player who is not counting cards.
Practice the decisions until they are automatic with the blackjack trainer before applying them at a real table.
Frequently asked
What if I split aces and get another ace? Resplit if the casino allows it. If not, you play the ace-plus-ace (soft 12) hand according to the rules — usually one card only per split-ace hand. Check the table’s resplit policy before playing.
Can I double down after splitting? At most casinos, yes. Doubling after split is permitted and you should take advantage of it when basic strategy calls for a double on your new two-card hand. If the table does not allow DAS, your split strategy for pairs like 2s and 3s becomes slightly more conservative.
Is it ever right to split 10s? No. A 20 is too strong to dismantle. Card counters occasionally split 10s in very specific positive counts, but that is an advanced technique entirely separate from basic strategy — and it is still done infrequently even by counters.
Does the number of decks change the split strategy? Slightly. In single-deck games a few borderline pairs (like 6s vs. a dealer 2) shift at the margins, but the core rules — always split aces and 8s, never split 10s and 5s — hold across all deck counts.
Sources & further reading
- Wizard of Odds — Blackjack — basic strategy tables and expected-value analysis by pair (accessed June 2026)
- LearnTheOdds — Blackjack Basic Strategy Math — full EV calculations behind every decision category
- LearnTheOdds — Play Blackjack — free practice game to drill split decisions
Educational explanation only. No real-money gambling happens on LearnTheOdds.
Responsible gambling: Play for entertainment, not income — the math favors the house over time. Set limits, never chase losses, and if it stops being fun, take a break. 21+. Need help? Call 1-800-MY-RESET (1800myreset.org).