Pair splitting in blackjack is a way for players to reduce the house edge against them. However, a playing option that was meant to help players often results in a moneymaker for the casino. The reason is that most players split pairs recklessly, or rely on hunches, with no thought towards proper strategy. But it doesn’t have to be this way.

The casino rules for pair splitting are easy to understand. If you are dealt two cards with the same value, you have the option to split them into two separate hands, each with its own wager. For example, if you bet $10 and are dealt a pair of 3s, your initial hand totals 6. You could either play the hand as a 6 and draw additional cards, or you could make another $10 bet and split the 3s into two hands (with each hand starting with a 3). Unlike doubling down, you cannot split a pair for less money than your original bet. (If your initial bet is $10, you must put up another $10 on each additional hand.)

Most casinos allow players to resplit, meaning they allow players to split their cards more than once. For example, suppose you bet $10 and are dealt a pair of 6s; you bet another $10 and split, and you draw another 6. You can split again, and you would have three $10 bets riding on three independent hands, each starting with a 6. Some casinos also allow players to resplit twice, creating a total of four hands (the original split plus two more resplits); whereas, other casinos limit players to only one resplit, for a total of three hands (the more times you can resplit, the better it is for you).

The rules for splitting aces can also be different from one casino to another. Most casinos will allow you one hit per split ace (meaning, you can’t resplit, which hurts you if you draw another ace to a split ace, as now you are stuck with a 12). Casinos with more liberal rules will allow players to resplit aces. Most casinos will also allow you to split any two cards with a value of ten (e.g., a Jack-Queen or a 10-King); however, splitting 10-value cards is one of the worst possible plays a player can make.

Finally, most players think they have a blackjack if they draw a 10 or picture card to a split ace. Not so. They have 21, but they will be paid even money (assuming the dealer doesn’t have a blackjack or 21). You get a 3-2 blackjack bonus payout only when the first two dealt cards to a hand total 21.

So when does it make sense to split pairs? There are three reasons why you would want to split pairs, instead of using an alternate strategy. You should always split when:

1. You win more money on average (bold strategy).
2. You lose less money on average (defensive strategy).
3. You turn a potential losing hand into a winning hand (offensive strategy).

Let me give you a few examples of how this works. (I’ll assume an initial wager of $10 in a six-deck game, dealer stands on soft 17, you are allowed to double down after pair splitting, and resplit up to a total of four hands.)

A bold strategy means you are already favored to win money on the hand, if you don’t split, but if you do, you’ll win even more money. For example, suppose you are dealt a pair of 9s and the dealer’s upcard is a 6. With a $10 initial bet, you can expect to win $2.81, on average, if you stand with 18. However, if you split the 9s, you can expect to win $4.64 on average. Therefore, splitting the 9s against the dealer’s 6 is more profitable by $1.83.

The defensive strategy of betting more to cut your losses is often confusing to players. Suppose you are dealt a pair of 7s against a dealer 2. A 14, you’ll agree, is a lousy hand. If you stand, you can expect to lose $2.89 cents on average, meaning you will lose money in the long run with this hand. Suppose you split the 7s and play two hands, starting with a 7 on each. You can expect to lose only $1.20 on average. Yes, you are still going to lose money when you split the 7s but is it better to lose $2.89 by standing or $1.20 by splitting? Go with the play that cuts your losses.

This is the most rewarding kind of pair splitting because, by splitting, you turn a potential losing hand into a winner. For example, suppose you are dealt a pair of 7s against a dealer 6 upcard. If you stand on 14, you can expect to lose $1.56 on average. However, if you split the 7s, you can expect a net profit of $2.49 on average. By going on the offensive and splitting, you’ve turned a hand with a $1.56 deficit into a $2.49 profit, for an overall gain of $4.05.

The following chart shows the groupings of the proper splits specified by the basic playing strategy (see Table 1) for the above six-deck game. For example, splitting 2s against a 2, 3, and 7 is a defensive strategy to cut your losses, while against a 4, 5, and 7 it’s an offensive strategy to turn a loser into a winner, and against a 6, it’s a bold strategy to win even more when you have the advantage. (You don’t have to memorize this table ... it’s for information only. The groupings for split hands will be different depending upon the rules and the number of decks.)