“Counting cards,” or “card counting,” is the name of a card gamie strategy that involves keeping mental track of what cards have been played and what cards remain in the deck. Card counting is most often used as a blackjack strategy, since knowing the probabilities of the appearance of different cards gives you a decent advantage against the House.

Card counting is not cheating. It’s a legal strategy that requires lots of practice and a set of genuine skills. Since blackjack is a skill-based game, there’s nothing intrinsically wrong about counting cards to gain a blackjack advantage.

Here are some details about card counting, how it is used, its legality in different gambling jurisdictions, and how it affects blackjack odds.

Blackjack Odds & Card Counting

If you can run even a basic card counting strategy, you’ve turned blackjack into what is called a positive expectation game. Positive expectation just means the odds are in your favor instead of the casino’s favor. Card counting turns perfect blackjack play (which gives the House a 0.5% edge) into a game likely to put money in your pocket. Card counters enjoy an approximate 1% advantage over the casino, depending on the card counting method, how closely they stick to their strategy, and the rules of the specific blackjack game they’re playing.

Betting Advantage for Card Counters

The biggest advantage card counters have is that they can make informed decisions about when to place large bets and when to pull back. When a blackjack game’s shoe offers advantageous conditions to the player, he increases his bets, and when the count turns the other way, he pulls back. This is also the number one way casinos identify card counters.

Long-term Gambling & Card Counting

Anyone can get lucky on a single pull of a slot machine lever or a single hand of blackjack, but long-term gambling at the blackjack table is really only a smart move if you’re counting cards. Basic blackjack strategies that don’t involve counting cards are great for the short term, but the built-in 0.5% edge blackjack has against even perfect strategy will beat you in the long run.

Here’s an example: you are placing $5 bets on 60 hands per hour and you play blackjack for 7 hours. That means 420 hands at $5 each, or a total of $2100 wagered. You can expect to lose 0.5% of that, so you’re likely to lose around $100. That’s just an average; you could hit a good streak or a bad streak or get lucky on one big hand, but statistically speaking, even with perfect strategy, the casino wins out in the end.

That same session when you’re counting cards and enjoying a 1% advantage means you can expect to win $200, instead of losing $100. This strategy turns a losing game into a game that pays you to play it. That’s why card counting is popular: it gives you an edge against the House.

Is Card Counting Legal?

In the United States, there are no laws against card counting. Counting cards is a legal strategy that is not considered cheating. Blackjack strategy isn’t illegal, and that’s all card counting is, a complex strategy for beating the dealer.

That being said, card counters are certainly at risk for being asked to leave a casino. Like any other business., a casino can ask you to leave for any reason. One you’re labeled a card counter, you might even get stopped at the door of a large casino. They keep records on card counters.

Card Counting and the Law

To understand a little more about card counting in casinos, let’s look at two states in America with big gambling jurisdictions. Nevada, home to Las Vegas and Reno, gives casinos the explicit right to ask card counters to leave the property. The justification is not all that complex: casinos have this right because of a legal precedent grounded in what is called “common law.” In Nevada, the precedent states that owning a piece of property means you can ask anyone you want to leave that property.

Lawsuits in Nevada on behalf of card counters suggest that asking card counters to leave is illegal discrimination. Card counters are just highly skilled blackjack players, not much different from the gamblers at slot machines.

But since the Supreme Court holds that only discrimination based on race, creed, gender, national origin, age, or disability is illegal, casinos can discriminate against card counters all they want.

In New Jersey, the law is a little more favorable to card counters. Lawsuits filed on behalf of one card counter in particular in Atlantic City led to big changes in state gaming law. Blackjack expert Ken Uston won a lawsuit that allows him and other card counters to use their strategy without fear of recrimination. The New Jersey Casino Commission decided to alter the rules of the game of blackjack in New Jersey rather than honor the demands of card counters, taking away most of the edge available to people who count cards.

Counting cards takes time and dedication to put into practice. Blackjack can be turned into a positive expectation game, but even using perfect strategy and keeping a count in your head doesn’t make you an automatic winner. Blackjack is still a skill game with a built-in advantage for the casino, and over time, even card counters risk losing their bankroll to the casino. There is no such thing as a can’t-lose blackjack strategy, even if you’re counting cards.