Basic Strategy on Doubling

30 January 2020

By John Grochowski

Whenever blackjack basic strategy charts list doubling down as the best available play, it means you’re in a profitable situation.

It doesn’t mean you’re going to win every time, of course. But on balance you’ll win money overall if you double on hard 11 every time the dealer has a 6 up, or double on soft 18 every time the dealer has a 5 up.

The situation is different with hit, stand and pair splitting decisions. Sometimes the recommended play will merely cut losses instead of turn a profit.

We stand on hard 17 instead of 10 not because we expect profit, but because we lose more often if we hit. We split 8s against 10 not because it’s a winning situation, but because we lose less money overall if we split every time.

Not all double-down hands are equally profitable. Some bring a healthy return, while some are barely in positive territory. But all are plays basic strategy players should make.

On average, hard double hands are more profitable than soft double hands. There are exceptions, but the 12 most profitable double-down hands are hard.

Assume a six-deck game in which the dealer hits soft 17 and you are permitted to double on any first two cards.

In order, the 13 most profitable double down hands are hard 11 vs. 6; hard 11 vs. 5; hard 11 vs. 4; hard 10 vs. 6; hard 11 vs. 3; hard 10 vs. 5; hard 11 vs. 2; hard 10 vs. 4; hard 11 vs. 7; hard 10 vs. 3; hard 10 vs. 7; and hard 10 vs. 2.

It should be no surprise that the list favors hard 11s, which can turn into 21s with one-card hits, and dealer cards near the middle of the deck – 6s, 5s and 4s – that maximize chances of the dealer busting.

The best of the bunch, hard 11 vs. 6, brings an average profit of 68 cents per dollar of your original wager, while No. 12, hard 10 vs. 2, brings 38 cents per dollar.

The most profitable soft doubling situation is soft 18 vs. a dealer’s 6. That’ll get you 36 cents per dollar of your original wager.

What about the least profitable end of the spectrum?

Those are mostly soft hands. Double on soft 17 vs. 3 and soft 16 of 15 vs. 4 bring an average profit of 6 cents per dollar of your original wager. The least profitable hard double. 11 vs. Ace, brings 12 cents per dollar.

In most cases, the margin between profits when hitting vs. doubling are wider on hard hands. The profit of 68 cents per dollar when doubling hard 11 vs. 6 is double the 34-cent average when hitting instead. In all of the top 12 hands, the average profit doubles when doubling instead of hitting.

There are diminishing returns, and the 12-cent profit when doubling hard 11 vs. Ace is only a penny better than the 11 cents when hitting.

None of the soft doubles bring average profits double those when hitting. The best soft double, soft 18 vs. 6, brings 36 cents when doubling vs. 22 cents when hitting.

At the bottom of the spectrum, we have to break the numbers down to tenths of a percent to see the advantage in doubling. With soft 15 vs. 4, the 6.4-cent profit when doubling barely edges the 6.1 cents when hitting.

I couldn’t blame a player near the end of his session bankroll from shying away. But no matter how small, any play that gives players an advantage is welcome.

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