Hard 11 — against almost everything. Hard 10 — dealer 2 through 9. Hard 9 — dealer 3 through 6.
Soft hands double when the dealer is weak, mostly 3 through 6. First two cards only.
What doubling down is
You double your bet and in exchange take exactly one card, after which you must stop. It is available only on your first two cards.
That constraint is the whole story. Because you get one card and no more, doubling only pays when that card is likely to make a strong hand and the dealer is likely to be in trouble.
Eleven is the best doubling hand
Ten-value cards are the most common card in the deck — 16 of 52. On 11 a ten-value card makes 21, and no card can bust you.
So hard 11 doubles against everything from 2 to 10. Only a dealer ace splits opinion, and that depends on the table rules.
| Your hand | Double against | Otherwise |
|---|---|---|
| Hard 11 | 2 – 10 (also A under H17) | Hit |
| Hard 10 | 2 – 9 | Hit |
| Hard 9 | 3 – 6 | Hit |
| Hard 8 or less | never | Hit |
Nine's range is narrow because a ten-value card only takes it to 19. That is not as strong as 21, so you press the bet only when the dealer is clearly weak.
Doubling soft hands
Soft hands cannot bust, so the risk in doubling them is smaller. But you still get only one card, which limits it to spots where the dealer is weak.
| Your hand | Double against |
|---|---|
| A,2 · A,3 (soft 13 · 14) | 5 · 6 |
| A,4 · A,5 (soft 15 · 16) | 4 · 5 · 6 |
| A,6 (soft 17) | 3 · 4 · 5 · 6 |
| A,7 (soft 18) | 3 · 4 · 5 · 6 (also 2 under H17) |
Doubling a soft 18 can look strange — 18 is a respectable hand, so why accept one card and stop? Because against a dealer 3 through 6 you are far enough ahead that pressing the bet is worth more than protecting the 18.
Three cards means no doubling
Once you have hit even once, doubling is gone — even where the chart prints a D.
An 11 built from 3+3+5 cannot be doubled; you hit it. Most published charts never mention this, which is why the calculator checks how many cards you hold and names the fallback play instead.
Double after split (DAS)
This rule lets you double a hand created by splitting. Tables that allow it are better for you; without it the house edge rises by roughly 0.14 percentage points.
DAS also changes some splitting decisions. A pair of fours, for instance, is split against a 5 or 6 only when DAS is available. The calculator's DAS toggle shows the difference.
Do not skip your doubles
Putting twice the money down feels risky, so players often hit instead. But doubling spots are among the few moments the player holds the advantage. Backing off there raises the house edge with your own hands.