How Hard Is It to Count Cards in Blackjack?

Blackjack Hand With a Numbers and Suits Background

Don’t ever mention the phrase “card counting” in a casino – unless, of course, you have no intention of counting cards. Casinos want you think counting cards is illegal (it isn’t), and they’ll call you a cheater and run you out of there on the vaguest suspicion that you’re involved in card counting.

This is the first in a series of blog posts I’m writing about counting cards in blackjack, and the focus of this first post is to discuss how hard it is to count cards in blackjack.

I’m not going to lie, either – counting cards in blackjack isn’t the easiest thing in the world to do – although it isn’t as hard as you might think, either.

Understanding Advantage Play and Blackjack

Blackjack card counting is simple in theory, but putting into practice and combining it with a specific mindset is harder.

That mindset is called “advantage play.”

In gambling, advantage play is when you place bets where you’re getting the best of it mathematically. In all casino games, the house has a mathematical edge. In some games and situations, you can change the way you play to tilt that math in your favor.

Blackjack Dealing Dealing Cards

That mindset usually includes being unwilling to ever make a wager where you don’t have an advantage. Recreational gamblers, by definition, aren’t playing with a mathematical edge against the house. I do know some card counters who are still willing to put money down at the craps table or the roulette table.

Such card counters don’t qualify as advantage players even though they sometimes use an advantage play technique during a specific game.

And, of course, the most famous advantage play technique in the casino is counting cards.

The Importance of Basic Strategy

One of the common misconceptions among casino gamblers and real money blackjack players is that you can get an edge over the casino just by playing each hand correctly. The correct play for every possible situation is called “basic strategy,” and you must master basic strategy before counting cards.

But basic strategy alone won’t give you an edge.

It just brings the house edge down to the lowest possible number.

You might play in a blackjack game where the house edge for the game is 0.5%, but if you’re making several basic strategy mistakes, you might bring the house edge up to 2% or 3%. You’re giving money to the casino if you do so.

Basic strategy is based on your two cards and the dealer’s up-card. You can choose to double, hit, split, stand, or surrender. One of those choices is always mathematically better than all the others.

Basic strategy has been computed and tested repeatedly with computer simulations. The game conditions affect a small percentage of situations, but any basic strategy chart is usually almost completely accurate.

Is mastering basic strategy hard?

It depends on how good at memorization you are.

But even someone who’s bad at memorization can eventually master basic strategy.

You MUST master basic strategy before even considering counting cards.

The History of Casino Card Counting

Dr. Edward Thorp is considered the father of card counting. He read an article called “The Optimum Strategy in Blackjack” while he was still a professor at UCLA. This article was written by Roger Baldwin, Wilbert Cantey, Herbert Maisel, and James McDermott. (They subsequently became known as “The Four Horsemen.”

In that article, the authors created and explained both basic strategy and card counting. Dr. Thorp took the basic theories in that article and refined them with computer simulations. The idea was simple enough – what effect does removing a specific card from a deck of cards do to your odds?

If you don’t intuitively understand why removing a card from a deck would matter, consider this – what if all the aces from a deck have already been dealt?

What happens to your probability of getting a blackjack?

Ace and Jack of Spades

If you’re playing in a single deck blackjack game, your probability of getting a blackjack drops to 0%. It’s impossible to get such a hand without an ace.

And, since a blackjack pays off at 3-to-2 instead of even money, the house edge increases in this situation.

The next leap in logic isn’t huge. The fewer 10s you have in the deck, the lower the probability of getting a blackjack becomes. After all, you need a 10 and an ace to get a blackjack. There’s no other way.

Removing those 10s has other effects, too. It means that doubling down and splitting become less profitable, too.

Thorp used this line of thinking to develop the first formal card counting system – “the tens count.”

How to Use the Ten Count System That Edward Thorp Used

I should point out that the ten count is not the optimal card counting system to use. But, since it was the first, it might be illustrative to talk about how to use it.

The first step to using this card counting system is to memorize blackjack basic strategy and commit to make every playing decision based on basic strategy. You then keep a running count that reflects the ratio of high cards to low cards in the deck. Each card has a value that you add or subtract from the running count.

Every time a low card gets dealt, your edge increases. Every time a high card gets dealt, your edge decreases.

In the ten count system, the 10s, jacks, queens, and kings are the high cards. You count them as -9 each.

All the other cards in the deck – including the ace – count as +4.

You start with 0 and move the count up or down based on the +4s and -9s.

When your count is 0 or lower, you should bet as little as possible. When the count is +1 or higher, you should bet more. The higher the count is, the more you should bet.

This system, by the way, is only useful when you’re playing in a single deck game. It doesn’t work well at all in games with two or more decks.

Does the ten count seem like a hard counting system to use?

If so, that’s because it is.

The Hi-Lo System for Counting Cards

A better system for counting cards, in terms of usefulness, is the hi-lo system. Unlike Thorp’s 10 count system, the only values you need to use when counting are +1 and -1, which makes the system exponentially easier to use.

In the hi-lo system, the low cards are 2, 3, 4, 5, and 6. Those cards all count as +1.

The 7, 8, and 9 are considered middle cards and count as 0.

The aces and 10s (including the face cards) count as -1.

Overhead View of a Blackjack Dealer

As with the 10 count, you start your count at 0 and move up or down by 1 depending on which cards are dealt. If you’re playing in a single deck game, you just use the running count to determine how much you bet.

If you’re playing in a game with multiple decks, you must convert the running count into the “true count.” You do this by dividing the running count by how many decks you estimate are still in the shoe.

This is a step that a lot of beginning card counters hate, but it’s not as hard as they think. A rough estimate is good enough to get an advantage over the casino house edge.

What Is a Betting Spread, and How Do You Bet?

Most card counting books offer specific strategies for raising and lowering the sizes of your bets based on the true count. The problem is that casino staff are familiar with the same books. If you count cards and raise the size of your bets “by the book,” you’ll get noticed right away.

The biggest tipoff to the casino that you’re counting cards is the size of your betting spread – that’s just a ratio of your lowest bet compared to your highest bet. For example, if you’re betting between $5 and $25, your betting spread is 5-to-1.

The bigger that difference is, the more likely you are to get heat from the casino. At the same time, though, the bigger your betting spread is, the more of an edge you gain over the house.

There are techniques you can use to camouflage that you’re counting. Keeping the betting spread small is one of them. Another is to only increase the size of your bet after winning a hand. Lots of players do this when they’re feeling lucky.

It’s also common for players to lower the size of their bets after losing hands, so you can do the same thing. The problem with those camouflage techniques is that they all cut into your edge over the casino.


Does counting cards seem hard based on what I’ve presented so far?

It’s not the easiest thing in the world to do, but it’s far from impossible.

In the other posts in this series, I’ll go into more detail about the intricacies of counting cards.