When you are dealt two of the same card number in blackjack, you can choose to split them into two hands. You will be dealt two more cards (one for each new hand). Your bet is doubled but you now have two chances to beat the dealer. Knowing when to split pairs in blackjack can add a significant amount to your expected return. And since there are only ten possible situations in which you can split cards, it’s not hard to memorize what to do in every single situation..
Just because a player can split does not mean that he should split. He should split only if it gives him a better chance of beating the dealer. In order to judge if that will be the case the player should assume that the next card drawn will have a value of 10. This is because there are sixteen cards in the deck of fifty-two cards that have a value of 10. This gives drawing such a card a probability of 31%. Therefore the player should figure out that by drawing cards with a value of 10 can he convert a weak hand into two strong hands.
Split aces and eights any time you get them. No matter what up-card the dealer is showing, splitting aces and eights is always correct.
Split fours when the dealer only has a 5 or a 6. Split a 4 when the dealer has the two weakest possible states.
Never split a five. When you see a pair of 5s, your reaction should be to forget that they’re a pair of 5s and remember that they’re a score of ten.Double down on a 10 against anything but a dealer’s 10 or A. So prepare to double down when you get two 5s.
Don’t split a ten unless you are counting cards and the count goes to six or higher. If it ever happens, if you’re counting cards and the count actually goes to 6 or higher – that’s six extra tens per remaining deck in the shoe. If there are two decks left, that means a count of +12., Split 10s against a dealer 5 or 6. But don’t hold your breath. A count that heavy is astronomically unlikely. This is assuming a hi-lo count (2-6 get +1, 10 and A get -1) or a closely enough related variation (such as two only gets half a point, but also seven gets half a point, which works better but is harder to do).
Split twos, threes, or sevens when the dealer is showing a two through seven. If the dealer has an eight or better showing, just take a hit.
Split sixes when the dealer is showing any card that’s two through six. If the dealer has a seven or better, just take a hit.
Split nines against the following dealer up-cards: 2-6, 8-9. If the dealer has a seven, ten, or ace showing, stand.