Contrary to popular belief, card counting systems are easy to learn and don’t require complex mathematics.

For those of us not well-versed in casino strategy, card counting is something for math geeks and fodder for blackjack movies. Hollywood’s hyper-dramatized movie 21 led us to believe that learning how to count cards means immersing yourself in a world of sex, violence, intrigue and almost unlimited money.

Drama aside, card counting is not illegal, although getting caught doing it will get you banned from any casino. Lawrence Fishburne won’t drag you into a dark basement and beat you silly, but it’s best not make it obvious. We’ll get to that later. For now, an introduction to how it actually works.

How does it work?

You don’t need to be an MIT math wiz to be successful; a card counting system is built on a small amount of mathematical reasoning. The basic premise is to keep track of which cards have been dealt from the packs, so you can vaguely predict which cards will be dealt in upcoming hands.

You don’t have to do any complex equations. Each time a card is dealt you simply have to concentrate well enough to correctly add or subtract a number from the “running total.” The running total refers to the total of all of the cards you have counted. This number will help you predict what will be dealt in upcoming hands. In most games the dealers pulls from six decks, meaning that you have to count for a long time before the total has any meaning.

Consider this a “card counting for dummies”: assign a +1 to every card dealt between Two and Six. Assign 0 to cards Seven, Eight and Nine. Assign a -1 for Ten, Jack, Queen, King and Ace. You must count every card which is dealt from the pack, not just cards dealt to you. Let’s run through an example. The croupier deals a King (-1), Two (+1), Seven (0), Queen (-1) and Jack (-1). For those five cards, the running count is -2.

As the game progresses, the higher the number means that relatively more low cards have been dealt. This means that the chances of face cards coming out of the pack increases. Let’s say you are dealt a Ten and a Six. Under ordinary blackjack strategy hitting on a 16 would carry some risk. But if your count is negative, you can reasonably expect the next card to be low.

What are the consequences?

Unlike in the movies, card counting is more mundane than dangerous. As we’ve shown above, you just need to be able to pay attention and keep a count without making mistakes. Card counting isn’t illegal, it doesn’t involve entering some seedy Las Vegas underworld. In reality, it amounts to being really good at blackjack. If you are having a lot of success a croupier or pit boss may notice that you are counting and ask you to the leave the casino, and never come back.

Bear in mind that counting blackjack cards doesn’t always work. It helps you roughly predict what will be dealt in subsequent hands. There is no guarantee that your predictions will work. And it is not a big money enterprise for most players. Most blackjack tables involve relatively small bets, and counters must play successfully all night to build up a large bankroll. By one estimate, the average counter only makes around $20 hourly. If you are in need of money, don’t quit your day job.

Is 21 accurate?

I love Hollywood movies, especially when gambling is the subject matter. For the record I thought that 21 was excellent (anything with Kevin Spacey is brilliant in my book). But the film is just that: Hollywood. It was marketed as being “based on a true story” when in reality it was “vaguely inspired by a somewhat-true story.”

A group of MIT students did learn how to count cards and took regular trips to Vegas casinos during the 1990s. But most of the film’s drama never actually happened. For one thing, none of the players were interrogated or beaten. This doesn’t happen in Las Vegas. The closest story to it in recent years was when advantage player James Grosjean was handcuffed, detained and threatened in two separate incidents in 2000 and 2001. He received settlements in excess of $500,000.

In the film, main character Ben Campbell wins $315,000 in a single year. In the true story of the MIT counting team, players won on average $25,000 yearly. They weren’t placing outrageously large bets and winning almost all of them. Part of the reason that counters don’t make big money is that behavior like that is a certain ticket to getting noticed and booted out of the casino.

How difficult is it to do this?

As we’ve demonstrated, almost anyone can learn how to count cards. You need to learn a bit about blackjack, then apply a simple counting system each time you sit down at a table. Aspiring counters are advised to practice this at home until it becomes second nature. It isn’t difficult to do, but it isn’t particularly lucrative either.

You don’t always win, and even most successful counters only win marginal amounts for the amount of time they spend at the table. Most games are six deck blackjack, so you have to count for a long time before you can start to make predictions. It is something for blackjack enthusiasts to do on the side, not a primary source of income.