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# When and Why to Split Pairs in Blackjack

2 February 1998

Pair splitting in blackjack can be offensive, aggressive, defensive, or reckless. Offensive splits change expected results from losses to gains. Aggressive splits raise anticipated profits. Defensive splits lower potential losses. And reckless splits... well, don't do 'em.

Ordinarily, blackjack buffs follow basic strategy for splits without thinking about offensive, aggressive, and defensive situations. But, occasionally, after losing multiple bets rather than only one, or sacrificing what would have been a win to a loss or a push, bettors may question certain splits. And, players with depleted bankrolls may be tempted to avoid the added risk they perceive with this tactic. It's under such conditions that discerning the differences among the cases may be helpful.

Here are a few monetary examples. Values are per dollar bet at the beginning of the round. The figures are for six-deck games with doubling allowed on any two-card hands formed by the split, but no re-splitting into three or more spots.

Offensive: You're dealt a pair of sevens, the dealer has five-up. If you stand, you expect to forfeit an average of \$0.33. If you split, you expect to net an average of about \$0.12. Splitting converts a hefty potential loss into a modest likely gain.

Aggressive: You're dealt a pair of nines, the dealer has six-up. Standing with 18 is a reasonably strong position - expected profit is about \$0.28. But split the pair and expectation jumps to \$0.44. Splitting greatly improves the advantage.

Defensive: You're dealt a pair of threes, the dealer has seven-up. The book says "split." You figure you're damned if you don't and may be double damned if you do. The math validates the book. Hit and your expectation is to lose \$0.15. Split and you're still vulnerable, but expected loss drops to \$0.07. Splitting cuts the disadvantage in half.

The following list categorizes splits specified by basic strategy as offensive, aggressive, or defensive. Splitting any unlisted combinations of pairs and dealer up-cards is reckless. The guidelines are for multi-deck games with doubling allowed on any two-card totals after splitting but no resplits.

2-2: Offensive against four and five.
Aggressive against six.
Defensive against two, three, and seven.
3-3: Offensive against four through six.
Defensive against two, three, and seven.

4-4: Aggressive against five and six.
6-6: Offensive against five and six.
Defensive against two through four.
7-7: Offensive against four through six.
Defensive against two, three, and seven.
8-8: Offensive against two through seven.
Defensive against eight through ace.
9-9: Aggressive against two through six, and eight.
Defensive against nine.
A-A: Offensive against nine through ace.
Aggressive against two through eight.

Offensive splits rarely give players qualms. Aggressive splits sometimes cause the collywobbles because bettors know intuitively they're breaking strong hands. Defensive splits instill solid citizens with the most cause for pause. They lose more often than they win, and are memorable because the damage goes from one unit to two or more, depending on resplitting or doubling.

But gambling proficiency isn't about good or bad luck on a particular bet, or wishes you'd decided differently after the dust settles. It's about optimum choices determined by the laws of probability before you know the outcome. Kind of reminds me of the paradox posed by the perceptive poet, Sumner A Ingmark:

If past is prologue, future mystery,
Is only hindsight gained from history?

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Alan Krigman

Alan Krigman was a weekly syndicated newspaper gaming columnist and Editor & Publisher of Winning Ways, a monthly newsletter for casino aficionados. His columns focused on gambling probability and statistics. He passed away in October, 2013.
Alan Krigman
Alan Krigman was a weekly syndicated newspaper gaming columnist and Editor & Publisher of Winning Ways, a monthly newsletter for casino aficionados. His columns focused on gambling probability and statistics. He passed away in October, 2013.