Counting Cards in Blackjack

The History of Card Counting in Blackjack

The game of Blackjack began in France and Spain hundreds of years ago. On the other hand, card counting, also known as card reading or keeping a running count of the deck, began much later, in America.

An American named Edward O. Thorp experimented with counting cards in blackjack in the early 1960s using rudimentary computers and the belief that mathematics and a count were the secrets to gaining a competitive advantage. In 1962, he published a book called Beat the Dealer wherein he laid out a ten-count system based on card values (low cards and high cards) which, when counted, would allow a player to gain a slight edge and minimize the house’s edge. This book became a runaway hit and created generations of new blackjack players.

Thorp’s Hi-Lo Method Blackjack: The Running Count

Thorp’s strategy was based on a player’s ability to count cards. That is, counting value cards — high cards and low cards — and keeping a running tally to determine the true count. The concept is as follows:

In order to tally up cards, begin with two numbers in your head – 16 and 36 which represent tens in the deck and other cards in the deck, respectively. As the cards come out, you count backward, keeping a running tally by dividing your count of remaining “other” cards by the count of tens to arrive at the “Thorp Ratio” which would indicate player advantage and the best time to raise bets. Whether the running count was actually the true count was largely a matter of the players’ math abilities as well as other factors. Card counters, knowing they could tally up cards, popped up in casinos and grasped onto this strategy in the hope that they could take a bite out of the house edge.

Casinos, frightened by the prospect of card counters at their blackjack tables, and in an effort to avoid exposing the true count, changed their games to the use of two and four deck games, thus making it exponentially harder for players to tally cards or get a true count of the cards being shown. Thorp’s card counting method is now one of many in existence, and while casinos may have been scared of losing their edge to card counters, it became clear that the influx of new players coming to the game made it more than worthwhile for them to accept.

What is Card Counting?

Card counting in the game of Blackjack is simply keeping a running tally of all higher cards and low cards a player sees. By doing this, players get the chance to optimize their bets and perhaps gain knowledge of the true count. Card Counters are usually mathematically-inclined and are strategic players rather than “gut” players. This is a practice that is actually part of the curriculum at most dealer schools.

Why Keep a Running Tally?

Because of the fact that there is always an edge the house retains, that is the House always has an advantage over players, finding a way to minimize the house edge and get a chance to maximize wins is a major goal for gamblers playing a game of blackjack. Card Counting blackjack players, also known as “advantage players” like the practice because they can keep a running count and improve their odds by around 1%. While that may not sound like a big advantage over not counting cards, when a player is sitting for hours and playing many hands, this method could mean the difference between leaving with money in their hand or in the red.

Is Card Counting Legal?

As long as a player does not use any external card counting device when counting cards, or have another person or player assisting him, there is nothing illegal about keeping a running count of cards. It is, essentially, tracking the cards seen. Despite being legal, some casinos do try to impede the card counting player at their blackjack tables by using various methods including using more than one deck, employing hidden cameras, shuffling randomly, and instructing dealers to move the cut card to near the top of the shoe. In Nevada casinos, blackjack card counting is especially disliked by casino owners, and since the casinos are privately owned, card counting players who are observed by management will simply be asked to leave.

How to Count Cards in Blackjack: Thorp Method

There are essentially 4 steps to counting cards, or keeping a running tally of the cards, and one simple rule. This method, known as the High Low card counting system, assigns value based on the dealt cards – a high card and a lower card. That is, you tally your high cards and lower cards and based on their value, make bets accordingly. Here are the 4 steps, broken down.

  1. Assign a tag of +1 to every 2-6 ranked cards and a tag of -1 to every 10-A and tally up by the number to keep track of cards.
  2. Beginning after the dealer shuffles the deck, add the tags to each card pulled and keep a “Running Count” of the values of the card dealt
  3. After any round where there is a positive tally, the undealt cards have more high cards, so increase the size of your bet.
  4. When the running count is negative after any round, the undealt remaining cards have more lower cards, so decrease your bet.


Simply stated, bet more money on positive counts and less on negative counts. And that’s all there is to it. Track with a running tally of the cards, and make your bets based on whether the running count is positive or negative, thereby maximizing the amount of money you leave with.

True Count

To understand this better, you must understand what true count is. To calculate True Count, simply divide your Running Count by the number of decks left to be dealt. In a standard 6 deck blackjack game, each true tally will move the casino’s edge half a percent toward the player’s advantage. The concept of true count is one that must be understood to be able to use counting while playing. If the true tally is understood the rest of the strategy is simple.

Example: True Count and the Running Count

Here we will stop to discuss some examples of true count as related to running count. As an example, if your running count is -7 and there are two decks remaining to be dealt, the true count is -3. By further example, if the running count is +5 and there are 6 decks remaining, the true count is 0.83. And for a final example, if the running tally is +20 and there are 5 decks remaining to be dealt, the true count is 4. This means you should wager the running count and divide it by the number of decks remaining. As you can see, any remaining deck is a key part of determining true count. As you can see the running count and true count go hand in hand and learning how to get at the true count and running count is essential.

Dealing Shoe

A dealing shoe or dealer’s shoe is a device mainly used in casinos to hold more than one deck of cards and give the dealer the ability to have players dealt cards from different decks. In blackjack, where card counting is frequent, this practice can increase the house edge. Thus a dealer who uses a dealing shoe to deal the deck in casino’s wishing to discourage a player from counting, for example, is a common occurrence as the shoe uses more than one deck virtually insuring that it is impossible to keep track of card values.

Example of Another Counting System

Uston Advanced Plus-Minus System is an example of another Blackjack card counting system based on the use of a running count. It is very similar to the Thorp system but it does not have as many variables to be memorized. Here as each card in the deck is dealt, you will begin at zero and give 2 point cards a zero count instead of a +1 count like the Hi-Lo method does. Otherwise, the indexes are the same.

Level 3 Counting Systems

There are some blackjack card counting systems that truly challenge a player with mental ability and these are reserved for the most mathematically skilled among blackjack players. Using one of these to calculate a running tally with these systems, you will need to be able to add and subtract quickly and accurately and assign a value of 3 (plus or minus) to one or more cards all during play. Strategies like these can be learned but there is a little example that betting based on this level of counting will make the game more profitable in the long term and the simpler Hi-Lo running tally works nearly as well.


To look back, in blackjack there is a way to minimize the house’s advantage by keeping a running tally or a count of the cards seen. This playing strategy can be an effective method to use when determining a bet. As all gamblers want to minimize losses and maximize the money they take home, making bets based on the tally you have kept makes some gamblers feel they have an edge. By playing in this way, and betting with information on higher and lower through the use of one of the counting strategies can give a player a bit of an increased chance at this and when gamblers stay for long periods, remaining at the table for hours, the advantage might be profitable for them. For those players not remaining at the table for a long time, the practice may be less worthwhile. Casinos, never anxious to give up any of the house edge, may take steps to reduce or eliminate this practice.