Blackjack Strategy: When to Double Down
Blackjack is a game where the choices you make affect the house edge, particularly when doubling down or splitting pairs.
Both moves require an extra wager, so an incorrect decision can be costly.
When you double down, you double your original bet and receive one final card. When you split, you place a second equal bet and turn a pair into two separate hands.
Below, we show when basic strategy calls for each move and explain how differences in game rules at blackjack sites can affect those decisions.
Doubling Strategy at a Glance
To decide whether to double, compare your total with the dealer's visible card, known as the upcard.
A hard total has no ace counted as 11, while a soft total includes an ace that can count as either 1 or 11.
Hard Totals
Double hard totals only when you have 9, 10 or 11 and the dealer shows one of the upcards below:
| Total | Double Against |
|---|---|
| 9 | 3-6 |
| 10 | 2-9 |
| 11 | 2-10* |
*In a no-hole-card (European-style) game, hit hard 11 against 10 instead of doubling.
Soft Totals
Double soft totals only when you have 13 to 18 and the dealer shows one of the upcards below:
| Total | Double Against |
|---|---|
| 13-14 (A2 or A3) | 5-6 |
| 15-16 (A4 or A5) | 4-6 |
| 17-18 (A6 or A7) | 3-6 |
Does the Dealer Check for Blackjack Before You Act?
Whether the dealer checks for blackjack before you act affects how you should play hard 11 against a 10-value upcard.
In a peek (American-style) game, the dealer receives a face-down second card, known as the hole card, and checks for blackjack before players act. If the dealer has blackjack, the hand ends. If not, double hard 11 against a dealer 10.
In a no-hole-card game, the dealer takes their second card only after players have acted. If the dealer has blackjack, the extra doubled stake is lost, so hit hard 11 against a dealer 10 instead.
Splitting Strategy at a Glance
Basic strategy calls for a split when playing the pair as two separate hands gives a better expected result than keeping the pair together. The dealer’s upcard determines how most pairs should be played.
Two rules are easy to remember: split aces and eights and never split fives or tens.
For the remaining pairs, split only when the dealer shows one of the upcards below:
| Pair | Split Against |
|---|---|
| Nines | 2-6 or 8-9 |
| Sevens | 2-7 |
| Sixes | 2-6 |
| Fours | 5-6 |
| Twos or Threes | 2-7 |
No-hole-card adjustments: Do not split aces against a dealer ace or eights against a dealer 10 or ace.
If doubling after splitting is not allowed: Split twos or threes only against 4-7, split sixes only against 3-6 and never split fours.
Why Split Some Pairs and Keep Others Together?
Why Split Aces and Eights?
Two aces form a soft 12, while splitting gives you two chances to begin a hand with an ace. A pair of eights forms a hard 16, one of blackjack's weakest starting totals, so splitting gives both hands a better chance to improve.
Why Keep Fives and Tens Together?
A pair of fives forms a hard 10, which is already a strong doubling hand. Splitting replaces it with two weaker starting hands.
A pair of tens gives you 20, one of the strongest totals in blackjack. Splitting throws away that advantage.
How to Play the Other Pairs
For the remaining pairs, you generally split more often when the dealer shows a lower upcard and keep the pair together against stronger cards.
Nines are the main exception because a total of 18 is already strong against a dealer 7.
Does the Number of Decks Matter?
The tables in this guide cover common four-to-eight-deck blackjack games, but one- and two-deck games change a few close doubling and splitting decisions.
For example, a hard 8 such as 5-3 is a hit in four-to-eight-deck blackjack, but single-deck strategy doubles against a dealer 5 or 6.
When doubling after splitting is allowed, two-deck strategy also splits sixes against 7 and sevens against 8. Single-deck strategy also splits threes against 8 and fours against 4.
If you play a one- or two-deck game, use a strategy table matched to the deck count and the other rules.
Check the Rules Before You Play
The decisions above can change according to:
- How many decks the game uses
- Whether the dealer checks for blackjack before you act
- Whether doubling after splitting is allowed
The strategy in this guide should not be applied to variants such as Blackjack Switch, Spanish 21 or Blackjack Double Exposure, which use different rules and strategies.
Blackjack rules can vary from one game to another at online casino sites, so check each game's information or help screen before playing.
For all decisions, including when to hit and stand, see our full blackjack strategy chart.
Blackjack Doubling and Splitting FAQs
What happens when you double down in blackjack?
You place an additional bet equal to your original wager and receive exactly one more card. You cannot take another card after doubling, even when the new card gives you a weak total.
Can you double down on any two cards?
It depends on the table rules. Many American blackjack games allow doubling on any initial two cards, while some European games restrict it to totals of 9, 10 or 11. Always check the rules before playing.
Should you always split aces and eights?
Under standard American blackjack rules, you should split aces and eights. In European no-hole-card games, do not split aces against a dealer ace or eights against a dealer 10 or ace because the dealer may still make blackjack.
Should you ever split tens in blackjack?
No. A pair of tens gives you a total of 20, which is already one of the strongest blackjack hands. Splitting replaces that strong total with two separate hands that are more likely to finish with weaker scores.
Can you double down after splitting?
Some blackjack tables allow doubling after a split, while others do not. This rule affects the correct strategy for pairs of twos, threes, fours and sixes, so check whether doubling after splitting is permitted.
Is it better to double down or split in blackjack?
They are usually not competing options. Splitting is available only when your first two cards form a pair, while doubling is based on your total and the dealer's upcard. The correct action depends on your cards and the table rules.
