Doubling down lets a player raise the bet by up to the original amount after seeing the first two cards, in exchange for receiving only one more card. It is usually worth considering when the player’s hand is strong, such as 10 or 11, and the dealer shows a weak card. Rules differ: some tables limit doubling to certain totals or restrict it after a split. Basic strategy tables set out the best times to double and are based on the math of each situation.
Example
A player holds 6 and 5 for 11 and bets 10. Doubling adds 10 more. The hand gets one card, and the total stake at risk is 20.