How Does Counting Cards Work?

Determine the running count

Counting cards in blackjack works by first determining the running count of a shoe. The easiest way to do this is to use a balanced counting system that assigns a point value to each card. Twos, threes, fours, fives and sixes have a value of +1; sevens, eights and nines have a value of 0; tens, aces and face cards have a value of -1.

The basic principal of card counting is keeping a running count of all the cards played. For example, if a two, six, ten, jack, queen, three, seven and four were played in a hand, the running count is +1.

Determine the true count

Card counting also works by determining the shoe's true count, which is a ratio of the running count to the number of decks remaining in the shoe. A typical blackjack shoe at a major casino uses eight decks and a typical hand with six players consists of between 14-20 cards. Using that the true count can be determined by dividing the running count by the number of decks left.

For example, if five hands with six people had been played, that would equate to roughly 100 cards, or two decks, being used. There would be six decks left so if the running count was +12, the true count would be 2.

Using the counts to your advantage

Card counting works by using your knowledge of the count to your advantage. If the running count is positive, it means more low cards have already been dealt, leaving a larger percentage of high cards in the deck. This is in the player's advantage because more blackjacks will be dealt and there are more bust cards in the deck for the dealer to draw when he/she hits.

When there is a negative count, there is a higher percentage of low cards. This favors the dealer because there are fewer bust cards to draw from.

The conventional wisdom is to bet more when the running count is positive and bet less when the running count is negative. The true count can tell you how hot or cold the deck is. The higher the true count, the more the deck is in the player's favor.

The aftermath

Card counting works because when properly applied it can tip the odds from the house's favor to the player's favor. In a typical game, a skilled player who is not counting has slightly less than a 50 percent chance of winning the hand, giving the house a slight edge. When counting cards, a player takes a point or two advantage over the house and is more likely to win big over a period of time.

Contrary to popular belief, card counting is not illegal because a mechanical device is not being used to manipulate the game. Should you win, and win big by counting cards, you are entitled to your winnings, but casinos, which are private establishments, can ask you to leave the gaming floor.