What is Card Counting and is it Legal?

Casino expert and author Stephen Tabone looks into card counting, explaining how it works and whether or not it’s legal to employ.
Player counting cards at the blackjack table

Card counting is a strategy used in blackjack to try to predict whether the next hand is likely to provide the player an edge or disadvantage over the dealer.

To do this, card counters keep track of the high and low cards that have been dealt. They then use this knowledge to modify their bets and playing styles.

Although card counting is legal, casinos are typically opposed to it. Indeed, some may even prohibit players that they believe are doing it. In this guide, I’ll explain everything you need to know about card counting.

How Does Card Counting Work?

The idea of card counting in blackjack to keep track of the distribution of high and low cards in a deck, so that you can figure out whether the remaining cards are more favourable to the player or the dealer. The idea is that the more high cards that are left in the deck, the better for the player. By keeping track of the proportion of high and low cards that have already been dealt, a player can theoretically gain an advantage over the house.

Here’s an example of how card counting works in practice:

  1. First assign a value to each card in the deck. For example, give a value of +1 to low cards (2, 3, 4, 5, and 6) and -1 to high cards (10, Jack, Queen, King, and Ace).
  2. Keep a count of the values of the cards that have been dealt. For example, if the first card is a 3, the running count would be +1. If the next card is a Queen, the count would go back down to 0.
  3. Use this running total to estimate the amount of high and low cards left in the deck. So if your count totalled +5, that would suggest there are more high than low cards left in the deck.
  4. Based on this number you can adjust your playing strategy to be more or less aggressive. If the count is a high positive number then you would bet more if you were following this strategy.

Note that the above is based on a game of blackjack being dealt at a brick-and-mortar casino. Bear in mind that most casinos will use between six and eight decks at the blackjack tables. Card counting at an online casino is not likely to be successful as there is effectively an infinite number of decks in use.

Is Card Counting Legal?

Card counting is not illegal, but there are lots of grey areas in the rule book. Many casinos view it as cheating, and they have the authority to ban anyone they believe to be employing this method. Gambling houses both online and offline can refuse players if they have justifiable grounds to do so. A player could even be charged with trespassing if they refuse to leave a casino after being discovered counting cards.

It’s important to note that while card counting itself is not prohibited, some card counting techniques might be. For instance, in some situations, people trying to scam casinos use a tool to aid with card counting. This could be a tiny camera or computer program. If they are caught using one of these methods, they could be subject to criminal proceedings.

How do Casinos Respond to Card Counting?

There are various ways that casinos have adapted to the issue of card counting, and their methods have evolved. If operators manage to identify a counter, they can ban them. However, they need systems in place to make it more difficult for people to do it in the first place.

Shuffling the Deck More Frequently

One of the most effective ways to combat card counting is to shuffle the deck more frequently. This makes it more difficult for the card counter to keep track of the cards that have been played and can significantly reduce the accuracy of their count.

Using Multiple Decks

Most casinos now use multiple decks in a single game to mitigate against card counters. Whenever you play a game of blackjack, you can check the rules to find out how many decks are in play.

Automatic Shufflers

Many gambling houses use machines to shuffle the cards, and this can make it harder for card counters to keep track of the cards. This is especially true with virtual games at online casinos, as these rely on random number generators rather than shuffles.

Collaborating with Other Casinos

When casinos ban card counters that they have identified, they may sometimes collaborate with other establishments, so they are prepared to deal with them. This means that when someone is discovered, they may find it difficult to pull the same trick at another casino.

Dealer laying down blackjack cards onto table.

How Effective is Card Counting?

Card counting can be an effective way to increase the chances of winning at blackjack, but it is not foolproof. The method relies on the idea that certain cards are more favourable to the player, while other cards are better for the dealer.

By keeping track of which cards have been played, the card counter can adjust their betting and playing strategy to take advantage of the remaining cards in the deck. However, it should be noted that this doesn’t guarantee a win. It only gives the player a small advantage over the house.

In Land-based Casinos

The system is only effective if the player can keep an accurate count of the cards, and it is most likely to be used in a land-based casino where they can see everything clearly. However, it can be difficult to do in a busy casino and there are cameras everywhere looking for people who are attempting it.

At Online Casinos

Card counting at online casinos is much harder than it is at land-based gambling houses. This is because they use state-of-the-art technology to mitigate against it. Virtual games use RNG, while live dealer games involve multiple decks and frequent shuffles.

Should You Use Card Counting When Playing Blackjack?

If you want to play blackjack here at Casino.com, it’s easy to sign up and start playing today. We recommend that you always play for fun and don’t take the games too seriously.

Stephen Tabone is a prolific author of books that analyse how casino-goers can profit from randomness. The London-born betting strategist has honed his expertise in number combinations and patterns for nearly 30 years, creating rule-based systems that reduce risk and raise long-term profits. His acclaimed Baccarat and Roulette books include the ‘The Ultimate Golden Secret Baccarat Winning Strategy’, ‘The Clockwork Betting System’, ‘The Ultimate Silver Bullet Proof Baccarat Winning Strategy’, and ‘The Martingale-Tabone Fusion Betting System’, among others. His other interests are in similarly high-stakes fields such as political analysis, investment and stock trading.

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