When to Split in Blackjack
Split when two hands that each start with one of your cards are worth more than the hand you hold. For most pairs that depends on the dealer's upcard. The table below shows, for every pair and upcard, how much splitting gains or loses compared with the best other play.
The short answer
- Always split aces and 8s.
- Never split 5s or 10s. Play 5,5 as a hard 10 and stand on 10,10.
- Split 9s against 2 to 6 and against 8 and 9. Stand against 7, 10 and an ace.
- Split 7s against 2 to 7.
- Split 6s against 2 to 6.
- Split 2s and 3s against 2 to 7.
- Split 4s only against a 5 or 6.
This is for tables where you can double after splitting and the dealer checks for blackjack. Other rules change a few of these; see how table rules change it.
What splitting is worth, pair by pair
Each cell is the expected value of splitting minus the expected value of the best way to play the pair without splitting. A positive number means splitting wins more, or loses less, over the long run.
| Your pair | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | A |
|---|---|---|---|---|---|---|---|---|---|---|
| A,A | +0.39 | +0.42 | +0.44 | +0.46 | +0.47 | +0.30 | +0.26 | +0.23 | +0.25 | +0.17 |
| 10,10 | −0.27 | −0.24 | −0.20 | −0.16 | −0.11 | −0.26 | −0.40 | −0.53 | −0.50 | −0.54 |
| 9,9 | +0.07 | +0.10 | +0.13 | +0.17 | +0.20 | −0.03 | +0.11 | +0.09 | −0.12 | −0.02 |
| 8,8 | +0.30 | +0.33 | +0.36 | +0.39 | +0.42 | +0.63 | +0.37 | +0.10 | +0.05 | +0.02 |
| 7,7 | +0.13 | +0.17 | +0.22 | +0.27 | +0.31 | +0.23 | −0.02 | −0.12 | −0.16 | −0.23 |
| 6,6 | +0.04 | +0.10 | +0.16 | +0.21 | +0.26 | −0.04 | −0.13 | −0.23 | −0.29 | −0.30 |
| 5,5 | −0.55 | −0.52 | −0.49 | −0.45 | −0.41 | −0.58 | −0.63 | −0.66 | −0.64 | −0.67 |
| 4,4 | −0.14 | −0.09 | −0.04 | +0.01 | +0.07 | −0.21 | −0.23 | −0.26 | −0.32 | −0.32 |
| 3,3 | 0.00 | +0.04 | +0.09 | +0.14 | +0.19 | +0.08 | −0.01 | −0.12 | −0.18 | −0.20 |
| 2,2 | +0.02 | +0.05 | +0.09 | +0.14 | +0.19 | +0.08 | −0.01 | −0.12 | −0.19 | −0.20 |
Figures are in dollars per $1 of your original bet. Splitting is better, worse, close call (within 0.015 either way).
Splitting 8s against a 10 still loses, just less
8,8 is a hard 16, the worst total in the game. Against a 10, splitting returns −0.49 per $1 of your original bet, counting both hands. The best alternative, hitting, returns −0.54. You lose money either way, but splitting loses 5 cents less.
Against an ace the margin is thinner: −0.53 for splitting against −0.54 for hitting.
Why 5s and 10s stay together
5,5 is a hard 10, one of the best hands to double. Against a 6, doubling the 10 is worth +0.56, while splitting it into two hands that start with a 5 is worth +0.16.
10,10 is a 20, which already wins most hands. Against a 6, standing is worth +0.68 and splitting +0.56: two hands starting with a 10 are good, but not as good as one 20.
The close calls
These splits are within 1.5 cents per $1 either way:
- 4,4 against a 5: splitting is better by 0.013. The chart says split.
- 3,3 against a 2: splitting is better by 0.003. The chart says split.
- 3,3 against an 8: splitting is worse by 0.012. The chart says hit.
- 2,2 against an 8: splitting is worse by 0.015. The chart says hit.
The chart follows the standard strategy for 4 to 8 decks. This table uses an infinite deck, which ignores the cards already dealt, so on a call this close either play costs almost nothing.
How table rules change it
- No double after split: hit 2,2 and 3,3 against a 2 or 3, never split 4s, and hit 6,6 against a 2. Those splits mostly pay because a split hand can become 10 or 11 and be doubled. See the no double after split chart.
- No hole card (European rules): hit A,A against an ace and 8,8 against a 10 or an ace, because a dealer blackjack would take both split bets. See the European no hole card chart.
- Dealer stands on soft 17: every split is the same. With late surrender and a dealer who hits soft 17, surrender 8,8 against an ace instead of splitting. See the dealer hits soft 17 chart.
How these numbers are calculated
The figures come from the same engine as the calculator on this site, using an infinite deck: every card is as likely as in a fresh shoe. Each split hand gets one card and is then played its best way, doubling included; split aces get one card each. The dealer hits soft 17 and checks for blackjack first, so the figures apply once the dealer has no blackjack. Resplitting is not modelled, which slightly understates what splitting is worth where resplits are allowed.