Card counting

Before you start yelling “It’s not illegal!”, yes, we know. Technically, there is nothing illegal about counting cards. Technically, it doesn’t count as cheating, either. Technically… But this age-old technique of trying to beat the house at the quintessential card game, blackjack, is frowned on by casinos. They do not like it if you count cards. They would prefer it if you stopped now, thank you.

No, they can’t prove it, that’s true. If you have a head for numbers and a good understanding of how card counting works, you could probably do it without being detected. Do we encourage that? Well… Look, let’s be fair here. We all know the house has the edge and will always come out on top. Is there any harm in stretching your brain a little to give the odds a little boost in your favour? Probably not. Just proceed with caution.

A brief history of card counting

Blackjack, as we know it today, comes from various card games, including the French Quinze, Italian Sette e Mezzo, and the later Spanish and French version, Vingt-et-un. When the game we know today was starting to take shape, there were a couple of crucial differences. Firstly, the player could not see which cards the dealer had dealt themselves. In addition, the dealer was permitted to make their own hit and stand choices.

Over time, this changed. Dealers had to hit on 16 and stand on 17. Players could see the dealer’s up card. These two factors made it considerably easier for players to actively try and outsmart and outguess the dealer.

Blackjack started to gain popularity throughout the New World and was played both legally and illegally throughout North America for much of the 1800s. By the 1930s, Las Vegas had begun to take shape, and suddenly there was a focused place for gamblers and mathematical geniuses to come together and try to outsmart the game.

There are many stories of card counters getting caught in Las Vegas from the 1950s onward. Four players named Baldwin, Cantey, Maisel and McDermott, who claimed to have beaten the house many times, even wrote a strategy and tips book which included keeping track of your cards.

The first real mention of card counting, however, came in Edward O Thorp’s book, Beat the Dealer, published in 1962. While it took him some time to devise and perfect, the system is devastatingly simple:

  • Keep the numbers 16 (representing the cards valued 10) and 36 (all other cards) in your head
  • As cards are drawn, subtract them from one or the other total, depending on their value
  • Now divide the number of other cards by the remaining number of 10 cards
  • This gives you the ‘Thorp ratio’, which is used to determine bets

The book was a huge hit, and casinos didn’t know what had hit them. They were prepared to strike back, until they realised that, despite the huge increase of people trying to beat the system, very few were actually any good at it. Nevertheless, they implemented a few changes. For example, this system works well with a single-deck game, but not with two or four decks, so the casinos doubled up. Decks were also shuffled earlier and more frequently. For a time, this worked well.

Over the next few decades, variations on this technique were tried out and perfected, bringing us to the version of card counting that is most popular today, based on the Hi-Lo methods (see more below). For a while, especially in the 1980s and 90s, there was an intense focus on casino security experts and catching out card counters. However, over time it has become increasingly clear that, despite the wild popularity of the books and movies about card counting, not that many people do it. And of those that do, only a small percentage are any good at it, and an even tinier percentage become experts.

Does that mean you can’t learn to count cards? Not at all! At a minimum, it is an interesting brain-stretching exercise, and at best, it’s a casino-beating strategy that could win you millions. Just don’t be too disappointed if you don’t turn out to be a mega winner. Counting cards may be simple, but it is difficult to master.

Poker varients

How it works

Card counting is a method of trying to beat the dealer for blackjack, Pontoon, and other games in the 21 family. These games have near-identical game play and rules, and all revolve around getting as close to the number 21 as possible without going over.

Step 1: card values

  • All cards ranked 2 to 6 receive a tag of +1
  • All cards ranked 10 to A receive a tag of -1
  • All other cards receive a tag of 0

Step 2: running count

  • At the start of the new shoe, start with a count of 0
  • As each card is drawn, add or subtract the tag value from the running total
    • Eg: K, 8, 3, A, 6 = -1, 0, +1, -1, +1 = 0 (the running count is 0)

Step 3: true count

  • Now, divide the running count by the approximate number of decks remaining in the shoe
  • Eg: if the running count is +3, and there are two decks remaining, the true count is 1.5

Step 4: placing bets

  • Counting cards is about probabilities. It isn’t guaranteed to tell you what card will come next. Using the true count to gauge probability and to therefore adjust your bets is a great strategy. This is done by multiplying your betting amount by the true count.

It’s worth noting that there are many different formulas published, both online and in books, to help determine your betting strategy. 

Learning to count cards

Before you begin…

Card counting has been around for several decades now, and the systems have been put through many tests and trials. There are hundreds of variations, each of which promises to possess the ultimate secret ingredient. In truth, the only real secret ingredient when it comes to card counting is practice, practice, practice. If you hope to use it successfully, it must be completely natural to you. If you’re sitting at a blackjack table, and everyone is waiting for you to do maths in your head, you will be caught out.

Anyone can count

You don’t need to be a genius to count cards successfully, no matter what Hollywood tells you. You simply need to be able to add and subtract small numbers quickly. Beyond that, it’s a matter of practice.

Counting systems

There are plenty of card counting systems available to the intrepid blackjack player, although most are based on some variation of the Hi-Lo system. Some of the best-known systems include:

  • Hi-Lo
  • Hi-Opt I
  • Hi-Opt II
  • KO
  • Omega II
  • Red 7
  • Halves
  • Zen Count


This is the simplest version of the strategy, as we described it above. While some players feel that simple is best, others find this version struggles to hold up in multi-deck settings. Nevertheless, it is considered a reliable, easy method to master. Because cards are assigned a +1, 0 or -1 value only, it is easier to keep the running count going.

Card face value             Count

2, 3, 4, 5, 6                    +1

7, 8, 9                           0

10, J, Q, K, A                  -1

Red Seven

Red seven works very similarly to Hi-Lo, with one crucial difference. Where the 7 in Hi-Lo has a count value of 0, this is only true for black 7s in this version. Here, red 7s also carry a count value of +1. While it is a small difference, adherents of this version find it just a little more accurate. That said, others find this extra layer of complexity unnecessary, or even intrusive.

Card face value             Count

2, 3, 4, 5, 6                    +1

7 (red)                          +1

7 (black)                       0

8, 9                               0

10, J, Q, K, A                  -1

KO (Knock-out)

This variation on Hi-Lo once again adds value to the number 7. However, in this case, all 7s are assigned the count value of +1, and only 8 and 9 are assigned 0. In practice, it involves exactly the same amount of effort and maths as the standard Hi-Lo system, and is therefore simple and effective.

Card face value             Count

2, 3, 4, 5, 6, 7                +1

8, 9                               0

10, J, Q, K, A                  -1


Yes, there are card-counting devices that exist, but they are illegal in most jurisdictions. While mental gymnastics doesn’t count as cheating, because it relies purely on your own ability, these devices are absolutely considered to be cheating and will get you banned from casinos, if not arrested. We will not be covering any of them here, as we strongly discourage CasinoPlay members from buying them.

 Are you ready to count cards?

Some will say that card counting is unethical, or even immoral. Others will tell you it’s a great way of ‘sticking it to the man’. Yet others revel in the sheer mathematical beauty of it. The question really is, are you prepared to spend the time and effort it requires to get good at card counting? While the basics are simple enough, it is a skill that takes time and practice to perfect. Trust us, the last thing you want is to try card counting for real money stakes and discover you’re actually quite bad at it. If it appeals to you, then commit to learning it like a craft.

Tell us what you think

Have you ever tried card counting? Do you have a preferred method? Has it ever gone really well or horribly wrong for you? Share your card counting stories with us and enthrall (or at least entertain) your fellow gamblers.

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