You’re holding 12, the dealer is showing a 4, and every instinct says take another card. Basic strategy says stand. The reason has less to do with your hand than with the dealer’s.
How a Hand Works
The aim is to finish closer to 21 than the dealer without going over. Number cards count at face value, face cards count 10, and an ace counts as 1 or 11. A hand with an ace counted as 11 is called “soft”.
The dealer gets two cards, one face up. That visible card is the upcard. You act first, and if you go over 21 you lose straight away, even if the dealer busts later. Equal totals are a push, and your stake comes back.
The dealer makes no choices. House rules say when to draw and when to stop, usually drawing to 17.
Hit, Stand or Double Down
To hit is to take another card. With 11 or less you can’t bust, so you always take one if you aren’t doubling. From 12 upwards, every card risks pushing you over.
Standing means keeping what you have. Basic strategy stands on any hard 17 or more, and on hard 13 to 16 when the dealer shows 2 through 6.
A double down doubles your bet in exchange for exactly one more card. It suits strong starting totals: 11 against anything but an ace, 10 against 2 through 9, and 9 against 3 through 6. Some tables only allow it on certain totals.
Why the Dealer’s Card Matters
The dealer has to keep drawing until reaching 17, so a weak upcard is a problem for the house. Showing a 5 or 6, the dealer busts roughly two times in five. Showing a 10, a little under one time in four.
That’s why the same 16 calls for different moves. Against a 6 you stand and let the dealer take the risk. Against a 10 you hit, because standing on 16 loses whenever the dealer doesn’t bust.
Basic strategy comes from working out the expected result of every choice against every upcard, and course notes such as MIT’s appendix on the mathematics of card games set out the same rules, including standing on 12 against a 4, 5 or 6.
When the Rules Change the Answer
Basic strategy depends on the rules at the table. Hold 11 against a dealer’s ace and basic strategy says hit where the dealer stands on soft 17, but double where the dealer hits it. A dealer who hits soft 17 also adds about 0.2 percentage points to the house edge, the casino’s built-in advantage over the long run.
Other rules move the numbers too: how many decks are used, whether you can double after splitting a pair, and whether you can surrender, giving up half your bet to end a bad hand early. These rules can vary between online blackjack games, and a strategy chart only works for the rules it was made for. If a game only allows doubling on 10 or 11, you won’t get that option when you hold 9.
What Strategy Can’t Do
Even played perfectly, basic strategy leaves the house with an edge, roughly half a percentage point under common rules and more where the rules are worse. Short sessions swing a long way either side of that, and no decision can win back money already lost.
A strategy chart has an answer for every hand you can be dealt. How much to spend and when to stop are for you to settle before the first one.
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