Blackjack, also called twenty-one, is one of the most popular casino games. Despite the popular belief that you have to be a genius to count cards, anyone can count cards in blackjack with a little effort and enough practice. Counting cards is an easy skill to learn, but difficult to master. Although it is believed to be illegal by most people, its just frowned upon by casinos, but more to that later.

Card counting in blackjack is based on a simple principle: If there are more high cards than low cards in the remaining stack of cards, your advantage over the casino increases. Conversely, if there are more cards of low values, the edge of the casino increases. When applying the strategy right, the advantage of the player can often reach 2% or more. Which is quite good considering that the advantage of the casino is around 0.5% when using the basic strategy and 2% when using no strategy at all. By learning the basics of card counting you can improve your blackjack skills and increase your chances of winning and hitting it big.

What is card counting?

Card counting is a technique used to find out when the advantage shifts in your favor. If there are more high cards left in the dealer’s deck, the advantage is in your favor. If there are more low value cards left in the dealer’s deck, the dealer has the advantage. When applying the strategy, you increase your bets when you have an advantage and reduce your bets when the advantage goes back to the casino. By varying bets in this manner, gamblers can gain a positive advantage over the casino. However, keep in mind, that card counting is not for learning how to continuously win at blackjack, but rather an additional skill set to your normal strategy, to give you a better idea when to bet high and when not.

How does blackjack card counting work?

After the dealer shuffles the cards, there is an equal number of high and low cards in the stack. Depending on the cards dealt in the early rounds, the ratio of high to low cards in the remaining stack will change.

The basic strategy, also called Hi-Lo Card Counting, works as follows. First, assign tags to each card value as follows:

  • cards 2-6 get a tag of +1
  • cards 7-9 get a tag of 0
  • cards 10-A get a tag of -1

Now, you need to keep a running count which each card the dealer pulls from the stack using the tags mentioned above. If you manage to keep an accurate count as the cards are dealt, you will be able to monitor who is in advantage. You or the dealer. After each round, if the total sum is positive, increase your bet. Conversely, if the count is negative, reduce your bet. Thus, the higher the positive count and the more cards that have been played, the greater is the players edge and the more the player should bet.

Blackjack is most commonly played with 6 to 8 decks. Therefore, it is important to calculate the so-called True Count. To get the true count, simply divide the total sum by the number of remaining card decks. This is important, as having a running count of +4 with 6 decks remaining is completely different from having a running count of +4 with only 1 deck remaining. In the first example, there is less than 1 additional high card per deck remaining, so the player doesn’t have the advantage yet.

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Using the true count, each point reduces the house edge by approximately 0.5%. Therefore, the player has a significant advantage when the true count is 2 or higher. There are also other, more advanced card counting strategies, which will be explained in another post.

Can you count cards in online blackjack?

Basically yes, you can count card playing online, but it has become increasingly difficult, as most online casinos use software that shuffles the cards every time a new hand is dealt. Counting cards when playing video blackjack does not give you an advantage, as each game is played with a new virtual deck of cards. However, in live blackjack, in land-based casinos or in an online casino, it is possible to some extent to use card counting, to gain an advantage over the casino.

Is card counting illegal?

Despite what any casino would like you to think, card counting is not illegal or considered as cheating, as long as you only use your mind and no card counting device. But casinos know that card counters can lose them money and therefore, they are not welcome. If they detect a card counter, the use their right to deny service, stop the game and ban the player from the casino.

Large buy ins, high bet variations, table hopping, and large lifetime wins indicates casinos that someone is counting cards. To avoid being caught you should chat with the dealer, vary your bet only minimally and don’t stay too long at one casino or one table.


Casinos also use other methods to protect themselves from players using such strategies. They use methods such as cut card. This means, that only half of the cards are dealt. As the benefits of card counting are the highest towards the end, this method significantly reduces the profitability of card counting. Another option used to protect themselves is the use of continuous shuffling machines. These devices automatically shuffle cards after the completion of each round and therefore making card counting useless.

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