
Short answer: you should split 4s against a 4 shown by the dealer as the up-card if you’re playing single deck blackjack and can double down.
Do you split 4s against a dealer 4 for single deck blackjack?
Whether you should split a pair of 4s is not a straightforward decision because it depends on the availability of the doubling after pair splitting (DAS) rule. Most online casinos include this rule.
If you’re playing single deck blackjack, and you CAN double after you split a pair – meaning if you are playing a single deck blackjack game with the DAS rule – you should split a pair of fours if the dealer is showing a 4, 5, or 6. If you get an Ace or 5 through 7 after splitting, you are in a good position to double down because the dealer is likely to score lower or go bust.
However, if you are not allowed to double down after splitting your pair, you should take a different approach.
Playing 4s versus Dealer 4 in Multi-Deck Blackjack.
Splitting 4s against a 4 in Blackjack is not a recommended move in basic strategy (which applies to multi-deck formats of the game). Basic strategy is a mathematically proven strategy that maximizes your chances of winning based on the dealer’s upcard and the player’s hand value. Basic strategy charts show you should hit on 4-4 when the dealer shows a 4, 5, or 6 upcard. However, this strategy assumes that the player is playing a standard game of Blackjack with four to eight decks and a dealer that stands on soft 17.

Crucially, the decision to split 4s against a 4 depends on the number of decks in the shoe. In a single-deck game of Blackjack, splitting 4s against a 4 is recommended, as long as you can double after splitting (DAS). However, in a game with multiple decks, splitting 4s against a 4 is not recommended.
So, the decision to split 4s against a 4 in Blackjack depends on several factors, including the number of decks, the dealer’s upcard, and whether DAS is allowed. Basic strategy charts indicate that players should hit on 4-4 when the dealer shows a 4, 5, or 6 upcard. However, if the conditions are favorable, splitting 4s against a 4 can be a profitable move.
As with any move in Blackjack, it is essential to make an informed decision based on the circumstances and not rely on superstitions or hunches.
Here is the bottom line: If the DAS option is available for a pair of FOURs (a) multi-deck blackjack, split two 4s against a dealer’s 5 or 6, and for (b) single-deck blackjack, split two 4s against a dealer’s 4, 5 ,or 6, and double down on the 5 and 6,
Do you split 9s against the dealer’s up card of 5?
Yes. It would be best to split 9s against the dealer’s up-card of 5. The basic blackjack strategy dictates that you should consider splitting a pair of 9s if the dealer’s up-card is any numbered card except a 7. That is because the dealer is highly likely to have a ten-card as the down card, creating a hand of 17, so your nine-pair will win.

Even if the dealer doesn’t hold a ten-card, they have a significant likelihood of holding a hand with a 5 through 9 (aka a stiff hand). This hand has a high chance of busting. Splitting your pair of 9s versus the dealer’s 5 is a good move.
Should you split 4s in blackjack?
You should only split fours against the dealer’s 2, 3, or 4 if you are allowed to double down after splitting pairs. You should hit on four pairs against the dealer’s up-cards 5+. The strategy may change if you are using advantage-play strategies like counting cards.

Should you be splitting pairs of 9s against a 6?
Yes, you should split a pair of 9s against a dealer card of 6. If the dealer holds any numeric card other than 7, you should split your pair of 9s. This strategy works best on single deck games, but can deliver results for double deck and multi-deck variants.
