Lesson 6 of 10 · 4 min
Lesson 6: doubling down on 9, 10 and 11
Key takeaway: Double 11 against everything but an ace, 10 against 2–9 and 9 against 3–6. At no-hole-card tables, don’t double against a 10 or ace.
Doubling down means doubling your bet in exchange for exactly one more card. You do it when you’re already ahead: your total is strong and the dealer is weak. It doesn’t make you win more often, but when you win, you collect twice.
The three rules
- 11: double against any card except an ace. Any ten — almost a third of the deck — gives you 21. (If the dealer hits soft 17, double against the ace too.)
- 10: double against 2 through 9.
- 9: double against 3 through 6.
With 11 against a 6, hitting is worth +0.34 bets on average and doubling +0.68. That’s the difference between playing well and playing very well.
At European tables
With no hole card, the dealer may still have blackjack. If you double and they have it, you lose twice as much. That’s why at no-hole-card tables 11 against a 10 or ace is a hit, not a double. In Spanish casinos you can also only double on 9, 10 or 11.
Every case, with the numbers, in when to double down.