Doubling Down Calculator

Defaults are Player Total 11, Dealer Upcard 6, Soft Total unchecked. That is a hard eleven against a six, the strongest common double in six-deck S17 DAS. Submit. Double Down? returns Yes, and the rule-set row prints 6D S17 DAS. You are putting a second unit out to receive exactly one card. Against a six the dealer busts often enough, and eleven plus a ten is 21 often enough, that the extra unit has positive expected value relative to hitting for a single unit.

Keep Soft false and walk the hard chart with the same dealer 6: total 10 is Yes (10 doubles versus 2–9), total 9 is Yes (9 doubles versus 3–6), total 8 is No, total 12 is No. Move dealer to ace (enter 1) with total 11: No, because hard 11 does not double versus ace on this chart. Move dealer to 10 with total 10: No, because 10 only doubles through 9. Move dealer to 2 with total 9: No, because 9 skips dealer 2. Those three negative edges are the usual memory failures.

Check Soft Total and enter 18 versus 6. Soft 18 (Ace-7) doubles versus 3–6, so Yes. Soft 18 versus 2 is No (stand on the full basic-strategy chart; this doubling tool only answers the double question, so it returns No). Soft 17 versus 3–6 is Yes. Soft 15–16 versus 4–6 is Yes. Soft 13–14 versus 5–6 is Yes. Soft 19 is No. Soft 12 is No. Uncheck Soft before comparing to the default 11 versus 6 or you will be reading the wrong tree.

The tool does not ask whether the two cards are a pair. Pair doubles after a split are allowed under DAS, but you still need a total that matches a double cell. A split 8 that becomes 11 versus 6 is a double here; a split 8 that becomes 16 versus 6 is not. Enter the post-hit or post-split two-card total you actually hold.

A worked negative: total 11, dealer 1, soft false → No. Hit instead on the full strategy chart. A worked soft negative: total 18, dealer 9, soft true → No. The full chart would hit that Ace-7 versus 9; this calculator only says not to double. Use it as a binary filter, then look up Hit versus Stand elsewhere if the double is refused. Reload defaults (11, 6, hard) whenever you get lost; that cell must remain Yes.

Doubling down is the only common blackjack action that simultaneously raises stake and freezes the hand at one extra card. It is used when the two-card total is strong and the dealer is weak, or when a soft total can still be hit in spirit (an ace keeps the hand alive if the extra card is small) against a bust-prone upcard. The calculator answers a single question: does this total, this upcard, and this hard/soft flag match a 6D S17 DAS double cell?

The Baldwin 1956 tables already isolated doubles as EV-maximising on 11 versus nearly everything and on 10 versus moderate upcards. Thorp and Braun tightened the soft-double grid once computers could enumerate Ace-2 through Ace-7 against each upcard. Casinos later restricted doubles to 9–11 only, or forbade DAS, because unrestricted soft doubles and post-split doubles transfer a measurable slice of edge to a player who knows the chart. This tool assumes unrestricted two-card doubles and DAS, matching the suite label.

Purpose: stop the two folklore errors. One is doubling 12 versus 5 because “the dealer is weak”—hard 12 is a stand or hit, never a double on this chart. The other is refusing 11 versus 6 to “not risk two units.” The second is a bankroll preference; the chart still says Yes. Soft doubles are the third error class: players hit Ace-6 versus 4 when the cell is a double, or they double Ace-7 versus 9 when the cell is a hit.

Limits: one extra card only; you cannot double after hitting. The engine does not know if the table forbids doubling 8s or soft hands. It does not apply European no-hole-card penalties on doubles versus ace and ten. It does not model 21+3 or lucky-lucky side bets. It does not output the EV of doubling versus hitting; published simulators put hard 11 versus 6 among the most positive double EVs, and soft 13 versus 5 among the smallest.

Historically, doubling is also why DAS is printed on the strategy cards. Without DAS, split 8s that become 11 cannot take the extra unit, which in turn makes some pair splits less attractive. This doubling calculator does not recompute splits; it only classifies the total you type. Use it with the split calculator when the two-card total came from a split pair. Default 11 versus 6 hard remains Yes under 6D S17 DAS.

Doubling down is the unique common action that raises the stake and freezes the hand at exactly one extra card. The table stores Double when the expected settlement on two units after that single card exceeds the expected settlement of continuing on one unit with the ordinary hit-or-stand policy. Baldwin's 1956 tables already isolated hard eleven versus nearly every upcard and hard ten versus moderate upcards. Thorp and Braun later tightened the soft-double grid once machines could enumerate Ace-two through Ace-seven against each dealer rank. The rule set here is six decks, dealer stands on soft seventeen, doubling after a split allowed.

Hard doubles occupy three rows. Hard 11 doubles versus every upcard except an ace: the chance of drawing a ten-value card is high enough that a two-unit twenty-one dominates, except versus an ace, where dealer blackjack risk and dealer twenty-ones erode the extra unit. Hard 10 doubles versus 2–9; dealer 10 and ace are too strong. Hard 9 doubles versus 3–6, the bust-prone window; versus 2 the extra unit is not justified because the dealer completes too often, and versus 7 through ace a 9 that becomes 13–19 is a stiff more often than a 20. Hard 8 and below never double. Hard 12 and above never double: you would be freezing a stiff or a made 17-plus at two units.

Soft doubles exist because an ace counted as eleven can fall back to one, so Ace-six plus a five is twelve, not a bust. Soft 13 and 14 double versus 5 and 6. Soft 15 and 16 double versus 4–6. Soft 17 and 18 double versus 3–6. Soft 19–21 never double. Soft 12 never doubles. Dealer ace fails every soft window. Single-deck composition-dependent charts sometimes add Ace-eight versus six; this multi-deck stand-seventeen table does not. Dealer hits soft seventeen would slightly improve a few player soft doubles against a six in the literature; the grid kept here is stand-seventeen.

Worked defaults. Hard eleven versus six is Yes, the strongest common double. Hard eleven versus ace is No. Hard ten versus ten is No. Hard nine versus two is No. Soft eighteen versus six is Yes. Soft eighteen versus nine is No. Soft thirteen versus five is Yes, among the smallest positive doubles. After a split, the same totals apply when doubling after split is allowed: a split eight that becomes eleven versus six is still a double; a split eight that becomes sixteen versus six is not.

Assumptions. Two cards only; you cannot double after a hit. American peek. No surrender interaction. The table stores the decision boundary, not the dollar gap between doubling and hitting. Published simulators put hard eleven versus six among the most positive double means and soft thirteen versus five among the thinnest. Bankroll refusal of eleven versus six is a variance preference. The mean still prefers the extra unit.