The odds of getting a Blackjack (a natural 21) depend on the number of decks used in the game. In a single-deck game, the odds are about 4.8%, or roughly 1 in 21 hands. In a multi-deck game, like one with six decks, the odds decrease slightly to around 4.75%, or about 1 in 21.1 hands. These probabilities are based on random shuffling and dealing of the cards.