Supply the cash. If you have “speedy math skills,” the house doesn’t always have to win at blackjack. But for math to work in your favor, you’ll need to be patient—and bring “at least 400 times your standard bet” to the table.
Do the math. A classic method assigns points to each card that’s been played. Start with a count of zero and subtract a point for every 10, face card, or ace. For every card from 2 through 6, add a point. Count no points for 7, 8, and 9 cards.
Place the bet. Divide your count by the approximate number of decks left in the dealer’s stack. When the result is more than 2, the dealer is “rich with big cards,” and you have an edge.
Play it cool. “Don’t move your lips as you calculate” or jump ahead by betting too many chips. Counting cards isn’t illegal, but you can expect that a “suspicious pit boss will show you the door.”