How do you count cards in Blackjack?

30-second summary:

  • Is counting cards illegal? No, but casinos will take measures against it, so you need to cater for that in your counting cards blackjack technique.
  • Card counting gives the advantage of predicting the next card dealt, so you can adjust bets to maximize profit or minimize loss. 
  • The most popular and simple way of counting cards in blackjack is the hi-lo system.
  • Learning how to count cards is not about memorizing numbers but assigning a +1 value to a high card (10s, faces and aces) and -1 to low cards (2 to 6).
  • Some of the best blackjack card counting systems besides the hi-lo running count and true count include the Ace/Five and KO systems.  
  • Card counting may not be for everyone because it takes practice, bankroll management, emotional control and ability to avoid detection from the casino. We will let you decide whether counting cards blackjack is for you.

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What is Card Counting in Blackjack?

Card counting in blackjack is a skill that helps players tilt the odds even further in their favour. In one of the best card counting methods, players count the cards that left the dealer’s shoe. That way, they can predict if the next card will be a 10-value card or a lower one. The point of card counting blackjack is to decide when the player has the upper hand. And hence bet higher to maximise winnings from blackjacks and high-value hands.

For example, if all the aces were dealt already, you have no chance of getting a blackjack and would bet the minimum, and vice versa. Is counting cards illegal? No - but it is frowned upon by casinos, and you may be asked to leave the game or the casino in general. So if you want to learn how to count cards, read on - and keep it to yourself.

Most people think card counting is memorizing exactly which cards have been dealt out of the shoe, but not really. Think about it. When you play blackjack, having more Aces and 10-value cards (face cards and tens) left in the shoe is beneficial to you. So one of the most basic forms of card counting is just keeping tracking of the low card and high card ratio.

It’s not as difficult as you may think. However, many get put off learning how to count cards because they have a few misconceptions about how to count cards in blackjack and what actually happens. So let’s dispel those first before getting onto the different card counting systems. 

Blackjack Card Counting Truths

1. Card Counting isn’t Illegal

It’s perfectly legal to count cards, but casinos do frown upon it. You will not see casinos taking drastic actions, but they can ask you to stop playing blackjack or even leave the casino. At which point you need to just oblige.

2. You Don’t Need to be a Math-Whizz

Movies like Rain Main and 21 portray card counting as a difficult skill, but in reality, anyone can learn how to do it. Counting is just assigning a +1 or -1 tag. Yes, some counting systems may take time to master. But there are more modern methods that yield a smaller profit but are simpler to understand and take the average casino player just hours to grasp.

3. You Can Even Count in 6 or 8-deck Games

Card counting is simply tagging plus values and minus values, and you can do that with any number of decks. However, it does get trickier the more decks you add-in. When you add in ore decks you need to divide the count (running count) by the number of decks (true count) - more on that below.

How to Count Cards in Blackjack (21)

The ‘grandfather of card counting’, Edward O. Thorp, published a book in 1962 called ‘Beat the Dealer’. This is where he laid out strategies he created that allowed for optimal blackjack play. Today, the hi-low / points system by Henry Dubner has widely replaced Thorp’s 10-count system for beginner blackjack counting.

Hi-Lo is considered one of the standard blackjack counting systems because it’s easy to learn and it works. You simply assign a +1 value, or “tag,” to every low card (2 to 6) that is dealt from the deck. This signifies that their removal is beneficial for the player. Inversely, you assign −1 to the high cards (10 to Ace) to show that they are detrimental for the player. The neutral 7, 8, and 9 cards get a 0 tag because they have little influence on the player’s outcome.

For example, if 2, 3, Ace, 5 and Queen are dealt, the count would be: +1, +1, -1, +1, -1. The running count would be +1 so you would bet more. You can get some card counting practice by taking a deck of cards, turning each card over and assigning tags until you get to the end of the deck. The running count at the end should be zero since the deck is balanced in that way.

So to sum up the card counting basics:

  1. Assign one of the card counting values to each card dealt from the shoe (+1, 0, -1)
  2. Keep a ‘running count’ by adding or subtracting as they’re dealt
  3. Raise your bets as your count rises and lower them when it decreases

More Advanced Card Counting Systems

Hi-lo Extensions

Hi-lo is the easiest card counting system but alone it may not be the best card counting system for multiple decks. You will need to take the hi-lo strategy further and get a ‘true count’ alongside a ‘running count’. This is considered to be a more accurate card counting blackjack technique. We would use a true count when learning how to count cards with multiple decks.

A +6 running count in a single-deck game is not the same as in a multi-deck game because it contains more unseen cards. So to get a more accurate estimate, we need to turn the running count to a “true count per deck.” For example, if the running count is +6 with 3 unplayed decks, then the true count is 2 (+6 / 3).

Then there’s the addition of a +2 and a -2 in the blackjack card counting values, which starts to make it a more advanced card counting system. However, there are even more card counting techniques you can use at the tables.

The Ace/Five Count

In this card counting system, you set your own minimum and max bet sizes for the game and start with a running count of zero, just like hi-lo. Whenever a five is dealt, you add 1 to your running count, and when you see an Ace, you subtract one. If the running point gets to 2 or higher, you double your previous bet. But if it’s 1 or less, you stick to your minimum bet. This is great for 8 deck blackjack card counting and also considered the best card counting system for 6 decks.

The KO System

Unlike Hi-lo, the Knockout (KO) card counting system is unbalanced - meaning if you count blackjack values of all the deck, the result is not zero. But it turns out that an unbalanced system is the best blackjack counting system to use if you have trouble finding the more accurate true count. Perhaps because the accurate number of decks is not available. The blackjack card counting values are the same as hi-lo, except the 7 is considered a low card instead of neutral and so gets a +1 instead of zero. 

Should I go for Card Counting?

Blackjack is one of the more popular table games because of its significant house edge, And sure, a solid basic blackjack strategy will take you further. However, card counting improves your odds significantly and you know that not everybody is doing it. It’s a skill you can pair with your strategy to beat the dealer consistently in the long run.

It will take some understanding of this card counting article and frequent practice. Beyond that, you also need to be in control of your bankroll and practice effective money management. You should know not to overbet while card counting. Not only because you may get caught, but also because you should bet according to your bankroll.

Even more, if you’re a person that may get easily affected by negative swings at the table, because as we said, even card counters don’t win all the time. They just have a bigger advantage in the long-term. You also need to know how to avoid being detected for casino card counting because you may be asked to leave. So is it worth the effort? You decide. But if it is for you, then we hope you found this page useful. 

Key Takeaways

  • Card counting works because when there are more high-value cards in the shoe, you have a higher chance of making a blackjack (paying 3:2), splitting or doubling down. So, you can adjust your bet sizes accordingly to maximize profit or minimize losses.
  • The hi-lo system has replaced Thorp’s system because of its simplicity and adaptability to multi-deck games. It works by assigning blackjack values +1, 0, and -1 to low cards, neutral cards and high cards respectively. A positive count means to increase your bet while a negative count means to keep it minimum.
  • The hi-lo can be extended to two variations which make it even more accurate, but also more complex and one of the more advanced card counting techniques.
  • There are various card counting systems to try besides the hi-lo but the Ace/Five and KO systems cater for beginners too.
  • The Ace/Five count is one of the best systems for multiple decks while the KO system adjusts the hi-lo count in case you’re unable to find a true count.

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Blackjack Card Counting FAQs


Why is counting cards illegal in the casino movies we see? It actually isn’t. However, casinos do frown upon it and some may view it as an unfair advantage. The most that will happen is that you may be asked to leave the blackjack table or the casino altogether.


Card counting in Blackjack is a technique which helps boost a player’s odds of winning. You will count the cards that have been dealt from the shoe. This helps predict whether a high-value card or low-value card will likely be dealt next so you can adjust your bet accordingly.


Contrary to what many believe, learning how to count cards in blackjack isn’t about memorizing cards that come out of the shoe. There are various counting systems which you can find on this page, the most basic being the hi/low ‘running count’. You pick a value for each card (+1, 0, -1), track each card that has been dealt. Then assign the value to your count and adjust your next bet to be higher or lower. 


Honestly, there is a lot for the dealer to keep track of during a blackjack game. So it’s unlikely that they will also spend mental energy and focus on counting cards too unless they have a personal interest. But this would mean that they have been asked to do so by the casino or bribed in some way, in which case, you should leave that casino. 


The counting cards blackjack technique is meant to increase a player’s advantage. But it doesn’t mean that there’s no other way how to beat blackjack without counting. It’s still a game with a low house edge, so playing a solid game with moderate bet sizing may still work in your favour. Many try hole carding - identifying the dealer’s hole card before adjusting their play and beating blackjack without counting.