Card Counting in Blackjack

Card counting in Blackjack is almost a buzzword in the gaming community. Can you count cards? Is it legal? Is it worth it? All these questions are well covered here.

In short, card counting is not illegal, but there are some nuances that go against this practice. Find out how it works and if you can count cards in blackjack online.


What is Card Counting in Blackjack?

Card counting in the process of keeping track of what cards are left in the deck shoe. It’s very demanding, but a lot of players have mastered it with a lot of practice.

By knowing what cards are left in the deck, the player can make a better decision, whether to hit, stand, split or surrender.

When there are a lot of high cards in the deck (9,10 to A) the player is at an advantage, mainly because the odds of landing a natural blackjack are higher and the dealer is more likely to bust.

On the other hand, when there a lot of low cards (2-7), the dealer is at an advantage. This indicates to the player that they should be careful with their bets and play more conservatively.

In a nutshell, card counting enables the player to use statistic and real-time data to get an edge over the dealer. Card counting works great with basic blackjack strategy.

If you want dramatized representation of how blackjack card counting works, you should see the movie 21 with the now infamous Kevin Spacey.


How to Count Cards in Blackjack?

Understanding card counting is not the hard part, it’s as easy as learning how to play blackjack from the basics. The hard part is applying the process in practice. If done in actual casino with a real dealer at the table, you not only have to be focused, but you also must act natural and make decisions on the fly.

Here’s how you can count cards in blackjack:

assign value
Assign a value to the cards

In Hi-Lo, 2-6 have a value of -1, and 10-A have a value of +1.

assign value
Start the count after a shuffle

You start with 0 and you count what cards are out of the deck.

high count
High count

If there are a lot of low cards out, this means more high cards in the deck, the player is at an advantage.

low count
Low count

If a lot of high cards are out, you are at a disadvantage. There are fewer high cards in the deck.

bet during high count
Bet during high count

Place larger bets when the count is high. Odds of dealer busting are higher than usual.

This is how the process looks like in a nutshell. The rules are straightforward, but with so many distractions at the table, very few manage to do it successfully. You too can do it, and all you have to do is practice.

What’s Considered a High Count and What Low?

The high and low count are not set in stone. A high count has levels, and has different levels of accuracy at different levels of deck penetration (remaining decks in shoe). The low count, as a rule of thumb, is always an indicator to minimize your bets, or even leave the table.


In case it’s hard for you to grasp the idea and imagine how it looks in practice, here’s an example.

Let’s say the dealer just now shuffled the deck of cards. For the sake of education, this will be a single deck blackjack example. We are also going to assume that your basic bet is $5.

ActionCard Count ChangeCard Count TotalBet Amount
Dealer shuffles deck00$5
Cards dealt - 2, 5, J1+1-1=22$5
Cards dealt – 4, 4, Q, K, A1+1-1-1-1= -11$5
Cards dealt – 3, 2, 4, 7, 7,1+1+1+0+0 = 34$10
Cards dealt – 8, 9, 10, 3, 3, 40+0-1+1+1+1=37$15

At this point, the card count is high. This means that you can become more aggressive with your bets, taking advantage of the better odds of the dealer busting.

With enough practice, you won’t even notice you’re keeping track of the count. It will become second nature.

You can start increasing your bets when the count exceeds three. You can also increase it further if you reach a count of six or more.


How Does Card Counting Work?

Card counting relies on four pillars, four principles that once combined give you the upper hand against the dealer. Here we explain all of them in greater detail.

  • assign card values
    Assign card values

    Understand how each card affects the count. Cards with values 2-6 increase the count by 1, 7-9 are neutral and don’t change the count, and 10-A decrease the count by 1. These value numbers are taken from the Hi-Lo as a reference system. Values are different in more complex systems.

  • keep a running count
    Keep a running count

    It’s imperative to keep track of the running count. It’s literally the sum that you keep track of by adding and subtracting depending on the cards dealt. The running is the same as the true count in a single deck blackjack.

  • calculate the true count
    Calculate the true count

    The true count is the equivalent of the running count divided by the number of decks used. We need to have an unbiased ratio of low cards to high cards. This is how we account for the dilution of having more decks and more cards in the shoe.

  • increase or decrease bets
    Increase or decrease bets accordingly

    Bet management is key as with it you make up for lost bets when you didn’t know what the count is. This is how you make the profit. When the count is high enough, you should double the bet. If your budget allows it, you can even triple your bet.

You must do all of this with a ton of other distractions around you. The person next to you chatting, the dealer trying to have a chat with you, and ensuring you don’t spill your drink on the table. It’s very easy to get distracted and miss the count.

As a general rule, if you lose track, go with the first guess you have. Statistically, you’re more likely to be right than wrong. Remember, you can always stop, take a break, or even change the table.

As far as bet management goes, this is why table limits exist. It’s also a marketing thing, but table limits literally prevent one from betting super high during high count. And if you change the table, you must start the count from scratch when the dealer shuffles the cards.


Deck Penetration in Card Counting

The more data you have, the better the estimate you can make. In card counting, this is called deck penetration. The more cards are dealt, the better the estimate you can make of what the odds are for a high or a low card.

Card counting becomes effective when the deck penetration is 50%, with 60% being the threshold when you can see some significant results.

Here is how deck penetration works in practice:

If say the dealer has just shuffled the cards, you’re at 0% deck penetration. Let’s say it’s a 6-deck blackjack table. That’s a total of 52 x 6 = 312 cards in the shoe. The more players are on the table, the faster you are penetrating the deck. After 100 cards dealt, you are at 30% deck penetration. Once there are 150 cards out of the shoe, the card count becomes reliable.

It’s not the same to have a true count of +4 after a few hands, and after 150 cards dealt. Chances are, by this point, the count will be significantly higher, and you know for a fact that there are way more high cards than low in the deck.

Casinos and dealers prevent card counting by shuffling the decks before deck penetration reaches 50%. The moment the dealer shuffles the deck you need to start your count again from zero.


Does Card Counting in Blackjack Increase Your Odds?

Let’s assume that you have the ideal conditions to card count in a well-established casino. Let’s also assume that the dealer or the casino staff won’t bother you, meaning they won’t flag you for taking advantage of card counting.

Let’s also assume that you have the necessary budget to successfully apply and profit from blackjack card counting.

The answer is yes, card counting in blackjack increases your odds of winning by an extra 0.5% to 1.5% which is huge in the long run. Additionally, if the limits are not an issue, meaning you can increase your bet amount by a factor of more than ten with no problems, you are guaranteed to come on top and leave the casino with at least 1.5% on average.

Note, to have this success rate you should follow basic blackjack strategy at least and follow the Hi-Lo card counting system to the T.


Single Deck Blackjack vs Multi Deck Blackjack Card Counting

Blackjack card counting is much simpler in a single deck game. That’s because you never have to estimate the true count. In a single deck game, the running count is the true count, because the deck size is always 1 or less.

You can still try to get a better estimate if the deck is tens-rich or low-card-rich by dividing the running count by the number of cards remaining in the deck, but this can be extremely volatile. Single deck games are typically reshuffled after each game round.

For beginner practice, we recommend playing single deck blackjack online. It is much easier when you don’t have to constantly divide numbers after each hand.


Card Counting Systems in Blackjack

There are more than a handful of blackjack card counting systems, each with different level of complexity and of effectiveness. The less complex a system is, the less accurate it will be and vice-versa.

We singled out the most common and effective systems and divided them by complexity.

The most common system is the Hi-Lo. It’s considered the most balanced, and card counters begin learning using this system, and many experienced counters use it as well. The KO is also a good place for beginners, since it doesn’t require a True Count.

As you scroll down, you’ll find more in-depth info about each blackjack card counting system, how they work and their levels of complexity.


KO – Knockout System

The KO is the easiest, most beginner-friendly blackjack card counting system.

The main draw of this system is that calculating the true count is not required. You only need to keep track of the cards in play through the running count.

Card value systemCardsValue
Low card2, 3, 4, 5, 6, 7+1
Neutral card8, 90
High card10, J, Q, K, A-1

The running count does not begin at 0 using the KO, at least not in most cases. It depends on the deck size.

  • 1 deck = starting count is 0
  • 2 decks = starting count is -4
  • 6 decks = starting count is -20
  • 8 decks = starting count is -28

In a way, the KO makes up for the lack of a true count by inserting it beforehand, depending on the deck size. As usual, you should add, subtract or keep the running count intact, depending on what cards come out of the deck shoe.

The KO is simple, and least effective compared to more advanced systems. Nonetheless, it shouldn’t be completely underestimated. It helps ease beginners into card counting, but it can also show decent results in the long run.



The Hi-Lo splits all cards into three categories which have a different effect on the running count. It’s a simple system in theory, but it can be overwhelming in practice, especially for beginners.

With the Hi-Lo, the running count starts at 0. Every time you see a card corresponding to its category, you add, subtract, or leave the running count as it is.

Card value systemCardsValue
Low card2, 3, 4, 5, 6+1
Neutral card7, 8, 90
High card10, J, Q, K, A-1

The balance of difficulty vs reward in this system is excellent. Once you get used to it, you’ll see why many consider it the best all-around system for blackjack card counting.

If you master it to perfection, and combine its use with basic strategy, it will significantly impact your odds, while you apply less effort than more complex systems.


Omega II

The Omega II is a multi-level system where the running count can decrease by one or two value points. It’s more complex than the Hi-Lo, but with a higher accuracy.

We recommend the Omega II only for experienced blackjack card counters.

4, 5, 6+2
2, 3, 7+1
8, A0
10, J, Q, K-2

Just like in the Hi-Lo, the running count starts at 0 here as well. What’s more, card counters using the Omega II are advised to keep a count of the Aces left in the deck to estimate the odds of getting blackjack.


Wong Halves

Wong Halves is a multi-level system, and by far the most complex blackjack card counting system. The values here are fractional, and there are 6 value categories to keep track of.

Just keeping the running count here is challenging, let alone dividing it by the deck size to get the True Count, alongside all challenges card counting brings.

That’s why the Wong Halves is only recommended to expert-level players, those who’ve had hundreds of hours of experience in blackjack card counting.

3, 4, 6+1
2, 7+0.5
10, J, Q, K, A0

In Wong Halves, the running card starts at 0. As usual, you add, subtract, or keep the running count intact, depending on the cards coming out of the shoe.


What is The Best Card Counting System?

The best card counting system in blackjack will depend on your skill level and experience.

For a beginner, there are the KO and Hi-Lo. Experienced card counters can transition to the Omega II. The Wong Halves stands tall as the most complex and the most accurate system. However, it’s only recommended for players with years of card counting experience.

Card counting systems by difficulty
Most Beginner Friendly:

KO – Knockout System

Basic System:


Advanced System:

Omega II

Expert Level System:

Wong Halves

It is extremely advisable that you master systems one by one, starting either from the KO or Hi-Lo. Then, go upwards as you gain a natural insight and a strong instinct for the true count at any point in a Blackjack game session.


Is Blackjack Card Counting Illegal?

The straight answer is no. You certainly can’t get in trouble with the law for counting cards, but most casinos consider it “illegal” within their premises. Yet, the worst they can do is politely escort you out, ban you from the table, or ban you from their premises.

Casino operators can’t prove you counted cards, and they can’t take back what you’ve already won. If you get kicked out, it means you were successful, so we can hardly say it’s a terrible thing to happen.

Online, blackjack card counting is rare since it’s less effective. Some unverified information points to the fact that live blackjack tables have algorithms in place to detect and prevent card counters.

Yet again, the most an operator can do here is limit or ban your account. They cannot take away your winnings, unless they prove you cheated and broke the terms and conditions. That would be very unusual unless they can read minds. As far as anyone is concerned, all you did is play blackjack and win some money.


Can You Use Card Counting in Online Casinos?

To go in more detail about blackjack card counting in online casinos, it’s fair to say that it’s somewhat possible on live dealer blackjack tables, but not recommended.

The reason is simple. Card counting requires at least 50% deck penetration to show its effectiveness. To counter this, live dealers are instructed to reshuffle the deck at around 50% deck penetration.

Even with a sub-optimal deck penetration, card counting can be somewhat effective, but it’s simply not worth the trouble. In the long run, you could get a very small advantage even in live dealer blackjack. But your earnings margin would be extremely slim, and not proportional to the time, effort and money you risked.


Tips to Learn Card Counting Faster

There’s no magic trick that will make you a pro overnight, but these card counting tips can help you get where you want faster. The most important point we want to highlight is to master blackjack basic strategy, start with a simple system, and practice a lot before playing for real money.

  1. Master blackjack basic strategy – Professional card counters refer to basic strategy in majority of cases. It’s an absolute basic requirement for anyone aspiring to become a successful card counter. There comes a point in some game rounds where an experienced card counter should ignore basic strategy, but only in highly specific scenarios when the true count is high.
  2. Practice online – You can practice in keeping a true count using a blackjack card counting simulator. Don’t play “free play” or “demo mode” blackjack to practice since this software re-shuffles the deck after each round. There are simulators specifically designed for card counting.
  3. Start small – While learning the ropes, it’s best to start small and slowly increase your budget and bet size per round. Getting accustomed to blackjack card counting in practice is difficult, so save your budget once you develop a better instinct for the true count.
  4. Learn the KO or Hi-Lo system – Besides starting small, we strongly recommend mastering the Hi-Lo system as your basis for blackjack card counting. As a much simpler, but less effective alternative, you can start with the KO system. In any case, it’s best to start with the simpler systems before transitioning to more complex ones like the Omega II and Wong Halves.
  5. Avoid suspicion by managing bets – Avoiding suspicion is a skill by itself, separate from card counting, one that many professional card counters have expertly mastered. The basic way of doing this is by “faking” that you’re a normal blackjack player following basic playing patterns, by increasing your bet size after a win, and decreasing it after a loss.
  6. Play the right Blackjack variant – Blackjack card counting or not, you should always strive to find and play the best Blackjack version with the highest RTP and most favorable player rules. If you wish to practice on a single deck blackjack table with real money, you may have to deal with some unfavorable player rules. The single deck reduces a significant chunk of the house edge, so casinos compensate through by adjusting different rules.


Card counting in blackjack is a legitimate strategy that will increase your winning chances in the long run. The question is if the risk and time investment is worth your effort?

We don’t recommend card counting as a money-making method, even though that’s the only goal of this strategy. Consider that those hundreds of hours spent, and money risked practicing card counting, trying to get a 0.5%-1.5% edge over the house, can be spent in more productive ways.

If you want to become a card counter, start with the Hi-Lo or KO systems. Most players stop with the Hi-Lo, as it is the best all-around system. However, persistent players can master the Wong Halves to get the most accurate estimate and winning potential.

You should always keep in mind, the best “system” of increasing your winning chances in blackjack is mastering basic strategy, when we account for the balance of investment vs returns. It requires almost no effort since you can simply look at a basic strategy chart while playing and make your moves accordingly.



Yes, card counting really works but it requires specific conditions: favorable table that goes over 50% deck penetration, perfect mastery of complex card counting systems, as well as blackjack basic strategy, and a high investment of time and money in the long run. This is why card counters are rare.

The best blackjack card counting method is the Wong Halves in terms of accuracy, but it’s by far the most complicated one. It requires quick thinking and nearly instantaneous calculations of 6 different card categories, for as long as you’re sitting at the table.

Blackjack card counting, when perfectly implemented in the long run, can give you an advantage and make the RTP go between 100.5% to 101.5%. This slight, although very important advantage, is why card counters are immediately restricted or banned from casinos. There is no casino game with a natural player edge, and card counting is the only way to gain it.  

The question if card counting is illegal is common. If you are “caught”, meaning a casino heavily suspects you, casinos can kick you out for card counting. Not all of them to this, and it depends on a case-by-case basis. If you successfully count cards and win huge amounts of money, consider that you are probably the #1 threat on their radar.

Yes, card counting is difficult and requires long term play and to make it worth your while. That’s why so few people do it. The more you practice, the better you will get at it, but remember that card counting is not magic and provides a slight advantage over the casino.

Anyone can learn to count cards; the hard part is mastering it in practice. It takes a few hundred hours of experience until you develop an instinctual feel for the true count. There are also other factors to consider: ignoring distractions around you, avoiding suspicion, and managing your budget – all at the same time.

The easiest way to count cards is by using the KO – Knockout blackjack card counting system. This system is designed for absolute beginners and it doesn’t require keeping a true count. We instead recommend the Hi-Lo because of its increased accuracy. If you don’t wish to keep a true count, you can play Single Deck Blackjack using the Hi Lo.

The more complex system you use, the more accurate you will be at blackjack card counting. Of course, there is no system in the world that is 100% accurate. But the more complex systems like the Omega II and Wong Halves give reasonable estimates if the deck is tens-rich, when properly applied.

Basic strategy is based on the game rules, and it is not directly related to card counting. Professional card counters will always follow basic strategy, especially when the true count is low, and the deck penetration is moderate. There are certain exceptions when basic strategy should be ignored, but this instinct comes with years of experience and practice.

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