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# How to Play Soft 18 in Blackjack, and Why

10 March 1997

Soft 18 - ace plus seven - is one of blackjack's most frequently misplayed hands. Worse, it's a hand on which weak decisions may strongly erode expected returns.

The plethora of possibilities on soft 18 is what bedevils many blackjack buffs. It can be best to stand, hit, or double down - depending on the dealer's upcard and the house rules.

Even seasoned solid citizens sometimes squirm when doubling is indicated but interdicted. Then what? Hit? Stand? Such situations may occur when you start with two-five or three-four and pull an ace, for a three-card soft 18, but can double only on two cards. The dilemma may also arise when rules only permit doubles on hard hands. Or maybe you've split a pair of sevens against a dealer's six and draw an ace, but doubling after splits is a no-no.

The optimum decisions for soft 18, the reasons for them, and the penalties for deviating can all be seen in the accompanying table. The numerical entries show "expectation" - the net theoretical win minus loss - for the statistically-correct resolution of an initial \$1 bet. In the "decisions" column, "h" means hitting is least unfavorable, "D" means doubling is most favorable, "S" means standing is most favorable, and "(S)" means standing is better than hitting if doubling is prohibited. The table is for two-card hands in six-deck games, and shows expectations when the dealer does not have blackjack. The numbers change somewhat with circumstances, but the decisions stay the same. An exception is in games of two or more decks where the dealer hits soft 17; doubling then beats standing against a dealer's two-up.

Here's how to interpret the table.

Say you have a soft 18 versus a dealer's nine-up. The expectations are all negative, so you're an underdog one way or another. Stand and your statistically-expected net loss on a \$1 bet is over \$0.18, hit and it's just under \$0.10, double and it's more than \$0.28. Hitting is your least unfavorable alternative.

What if, instead, you have a soft 18 against a dealer's six-up? You're in the catbird seat, regardless. But, stand and your statistically-expected profit on a \$1 bet is \$0.28, hit and it's just over \$0.19, double and it's more than \$0.38. Doubling is by far most attractive. If you can't double, standing beats hitting.

How costly are improper decisions on soft 18?

A common error is to stand rather than hit when the dealer shows a nine, 10, or ace. These are adverse situations no matter what you do. Statistically, though, standing costs a \$10 bettor an extra \$0.84, \$0.37, and 0.05 per hand, respectively.

Another common error is to stand rather than double down against a dealer's three, four, five, or six. These are favorable hands regardless of how they're played. Statistically, though, failing to double trims the profits of a \$10 bettor by \$0.28, \$0.69, \$1.01, and \$1.02 per hand, respectively.

Soft 18 is a hand that separates the wheat from the chaff at blackjack. Playing it well doesn't necessarily bring pleasure in any particular instance, of course. But playing it weakly surely brings pain over a period of time. Sumner A Ingmark, the bettor's beloved bard, thought of it this way:

A sad tale, not a funny one,
He poorly played at twunny-one,
And rarely any money won.

 TABLE Expected net win or loss per \$1 initial bet for alternate decisions on soft 18 Dealer upcard stand (\$) hit (\$) double (\$) optimum decision A -0.1003 -0.0953 -0.3623 h 10 -0.1796 -0.1429 -0.3427 h 9 -0.1826 -0.0985 -0.2848 h 8 +0.1081 +0.0410 -0.0282 S 7 +0.4019 +0.1719 +0.2237 S 6 +0.2805 +0.1914 +0.3828 D(S) 5 +0.2031 +0.1520 +0.3041 D(S) 4 +0.1802 +0.1244 +0.2488 D(S) 3 +0.1511 +0.0907 +0.1793 D(S) 2 +0.1420 +0.0633 +0.1210 S

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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.