When to Double Down in Blackjack
Double hard 11 vs everything, 10 vs 2–9, 9 vs 3–6 — and don't skip the soft doubles: A-2 to A-7 against the dealer's weak cards. Doubling is the only move in blackjack where the casino lets you raise your bet after seeing you're a favorite. Take it.
Hitting, standing, and splitting are about losing less. Doubling is where you actually make money at blackjack — every double on the chart marks a spot where you are statistically the favorite, and the correct response to being the favorite is betting more.
The hard doubles
| Your total | Double against | Why |
|---|---|---|
| 11 | Everything (2–A)* | Any ten makes 21; you're the favorite vs every up-card |
| 10 | 2–9 | Same logic — but vs 10/A the dealer's start is too strong |
| 9 | 3–6 | Only into the dealer's bust cards |
*11 vs ace is a double when the dealer hits soft 17 (the common US rule); in S17 games, just hit it. The chart toggles both.
The flagship example, with exact numbers from our engine: 11 vs 6. Hitting earns +33.2¢ per $1. Doubling earns +66.5¢ — precisely twice as much, because you win the same percentage of hands with twice the money out. Even the "weak" double of 11 vs 10 (+18.0¢ doubled vs +11.9¢ hit) is real profit you leave behind by playing timid.
The soft doubles — where most money is left on the table
Players skip these constantly because "I have a 17, why would I double?" The point isn't your current total — it's that with an ace you cannot bust on one card, and the dealer's 4, 5, or 6 busts over 40% of the time (see the odds). Pressure with zero bust risk:
| Your hand | Double against |
|---|---|
| A,2 and A,3 (soft 13–14) | 5, 6 |
| A,4 and A,5 (soft 15–16) | 4, 5, 6 |
| A,6 (soft 17) | 3, 4, 5, 6 |
| A,7 (soft 18) | 2–6 (H17) · 3–6 (S17), else stand vs 7/8 |
| A,8 (soft 19) | 6 only, in H17 games |
Concrete: A-6 vs 6 — hitting earns +12.5¢, standing is a losing −0.6¢, but doubling earns +24.9¢ per $1. That's free money the table is offering anyone who knows the soft section of the chart.
Three doubling rules to remember
- 5,5 is a 10, not a pair. Double it vs 2–9 (+57¢ vs 6). Splitting fives is lighting money on fire (+16¢).
- Never double into a made hand. No doubling 8 or less, and no hard doubles vs 10/A except 11 (H17). The favorite-math has to actually be there.
- If you can't double, the fallback differs. "D" cells fall back to hit; "Ds" cells (soft 18–19 doubles) fall back to stand. The chart legend marks both.
Frequently asked questions
Why only one card when I double?
That's the trade: the casino lets you double your bet mid-hand, but you give up the right to keep hitting. The chart's doubles are exactly the hands where one card is all you wanted anyway.
Can I double for less than my original bet?
Usually yes — and you usually shouldn't. If the spot is worth doubling, it's worth the full double; betting less just shrinks a profitable wager. The only exception is bankroll constraints.
Should I double 11 against a dealer ace?
In H17 games (dealer hits soft 17): yes — it's a 21.5¢-per-$1 edge played as a double. In S17 games: just hit. This is one of only three cells that differ between the two charts — see the soft 17 guide.