To double down simply means you can double your original bet after you receive your first two cards. If you decide to double down you will then receive only one more card. Doubling Down is very profitable and lets you double your bet when you have an edge. The following charts show when you should double down for hard totals (a hand without an ace or where an ace is 1) for multiple and single deck games. There is also a double down chart for soft totals below.