As a highly popular casino game, blackjack is played by thousands of people but few of them are proficient in card counting. Even fewer manage to make a decent, sustainable profit from applying this technique when playing at the blackjack table. Successful card counters, on the other hand, are skilled at not only keeping track of the cards that have been dealt but also at properly structuring their bets in order to take a maximum advantage while remaining anonymous.
Once beginner players know the basic strategy for blackjack, they can start learning how to count cards. Contrary to popular belief, card counting is not a skill only exceptional individuals could master and it does not require players to memorize all cards in the deck. This is a technique that could be learned by most people and it allows them to identify the moment when the odds shift in their favor.
First Steps into Card Counting
Before blackjack players learn how to count cards like pros, they should obtain a good understanding of the game. Knowing the rules and the basic strategy is a must since even the best card counters would fail spectacularly if they do not build their playing tactics on mathematically proven moves and concepts. As an introduction into card counting, we have presented several fundamental ideas every blackjack player should focus on – what is card counting, how to determine the betting spread, and how is the Kelly criterion applicable to blackjack.
Fundamental Concept 
Bankroll and Betting Spread 
The Kelly Criterion Fundamental Concept
The concept of card counting in blackjack is quite simple – with it, players keep track of the ratio of high to low cards still left in the deck or the dealer shoe. They can do that quite easily by assigning values to different cards so that they always know whether the deck is rich in high cards or in low ones.
Since blackjack is formed with an Ace and a 10-value card, high cards (10, Jack, Queen, King, and Ace) are mathematically proven to work in favor of the player. Blackjacks simply pay 1.5 times the bet to the player and even money to the dealer; the dealer is required to Hit on 16 and stand on 17; the dealer is more likely to lose with more high cards in the deck.
So, if the deck has more high cards and blackjacks are more likely, the player has more to gain. Low cards, on the other hand, are known to favor the house. Typically, cards from 2 through 6 are considered low, whereas cards with a value of 7 through 9 are neutral since they are in the middle. Therefore, the more high cards are left in the deck, the better the odds for the player.
If we take a single-deck blackjack variation as an example (with no cut card and no burnt cards), we will start the game with 20 high, 12 neutral, and another 20 low cards. After several hands have been dealt, we may have a deck with 17 high cards, 5 neutral ones, and 12 low cards that have not been played yet. This means that the player has the advantage and in order to maximize his profits, he should place a larger bet.
This is the next important thing novices should remember – once they identify a deck with good odds, they should bet more. If the deck has 17 low against 12 or fewer high cards, however, the house has the advantage and players should keep their bets at the minimum. By following this principle, they will be able to win more on hands that are statistically more likely to win and lose less on hands that are likely to lose.
Bankroll and Betting Spread
The most important aspect of card counting and the one that actually helps players make money is the correct adjusting of the bet size based on the count they keep. If the count is high and suggests good odds, players increase the bet size and if the count drops, they reduce the amount of the wager. This variation in the bet size is known in blackjack literature as a betting spread (or bet spread).
The betting spread is different for each player as it depends on several things – the table limits, the maximum amount the player is willing to wager, and his or her bankroll. The bankroll is simply the amount of money dedicated specifically to blackjack play and it may be $100, $500 or $5,000 per session. Novices should start with a modest bankroll and a smaller betting spread to better understand the mechanics of the card counting system.
For instance, their betting spread is $5 – $100 so the lowest bet they will make will be $5 or 1 unit, while the highest wager will be $100 or 20 units. The same betting spread could also be expressed as 1-20. However, a 1-20 unit betting spread is an aggressive and a risky one and most players prefer 1-10 to 1-15 betting spreads. In fact, casinos would get suspicious if a player suddenly increases his bet 7 times after keeping his stakes at the table minimum for half an hour.
This is why choosing the proper betting spread is essential. Another reason that is at least equally important is the expected return from a certain betting spread, as well as the so-called risk of ruin that will be discussed in detail in the following sections.
The Kelly Criterion
There are various ways players can determine the proper bet size when playing blackjack and the number of units they should wager on high or low counts. One method that has been mathematically proven is the Kelly criterion, a principle that provides a balance between the risk and the potential reward. It was developed in 1956 by John L. Kelly Jr., a researcher in Bell Labs, and later used successfully in gambling and investment theory.
The Kelly criterion is a mathematical formula that determines what fraction of a bankroll should be wagered at any point during the game, based on several variables, including the likelihood of winning and losing. The formula is:
f = pb-q / b
Where f is the fraction of bankroll that we should bet per hand, b is the odds offered on the wager (b to 1), p is the probability of winning, while q is the probability of losing. Once all variables from the right side of the equation have been determined, we can easily calculate the bet per hand. Let’s assume, for instance, that the odds for the next hand are exceptionally good and the probability of winning is 75%, or 0.75. The probability of losing then will be 1-0.75=0.25 or 25% chances against the player. Here, b will be 1.5 (from 3:2 or 1.5:1, the payout for blackjack).
Based on these variables, the bet size should be 0.75*1.5-0.25/1.5 = 0.5833 or 58% of the bankroll, which is, of course, extremely aggressive betting. We can approximate the same Kelly formula as f = a/v, where a represents the player advantage, while v is for the “variance” of the game. Variance is the standard deviation squared. The standard deviation of blackjack is typically around 1.15 bets, although it may vary significantly based on the rules, so for our example, the variance will be 1.3325.
If the player calculates that, on a certain count, he has an advantage of 2% (0.02, which is quite high), and the variance is 1.3325, then f will be 0.02/1.3325 or 0.015. In other words, the bet size, in this case, should be 1.5% of the bankroll – if the player has a dedicated bankroll of $1,000, the proper amount he should bet here is $15.
Basics of Card Counting
As we have mentioned above, card counters do not memorize all cards that have been dealt so they can calculate exactly which cards are left in the dealer shoe. This is simply impossible in a fast-paced game such as blackjack, especially if 6 or 8 decks are in use. Instead, card counters estimate roughly the ratio of high to low cards in the shoe without knowing the exact cards that will be dealt next. The process of card counting can be broken down into four basic steps:
Assigning Values to Cards 
Keeping a Running Count 
Calculating the True Count 
Adjusting Bet Size 
Spotters 
The Big Player 
Avoiding Detection Assigning Values to Cards
There are more than a dozen methods for tracking the decks and counting the cards in blackjack but let us start off with the simplest, most straightforward counting system, the Hi-Lo. It distinguishes between three groups of cards – low (2-6), neutral (7-9), and high (A, 10). This system assigns the following values to these groups:
- 2-6 – +1
- 7-9 – 0
- 10, Ace – -1
Keeping a Running Count
The sum of the point values of all hands is exactly 0 and the Hi-Lo system is very easy to learn and apply. We start our counting with 0 and whenever a low card appears on the table, we add 1. When the dealer deals a high card, we subtract 1 from the count, while neutral cards simply do not affect the count at all. This is the so-called a “running count” and players should be certain of it at any point of the game.
When the running count is high (1 or more), this means that more low cards have been used than high cards since the beginning of the game. Therefore, the shoe consists of more high cards, so the player has the advantage. For instance, 3 players are betting against the dealer and their hands are – 7-4, 2-Ace, and Jack-6, while the dealer’s upcard is a 5. The running count in this situation will be +2, which suggests good odds for the players.
Calculating the True Count
So far, the Hi-Lo system seems simple and straightforward but to make counting of cards difficult, casinos use 6 or 8 standard decks of cards. This means that will be up to 416 cards at the beginning of the game. For this reason, players should take into consideration the number of decks used by converting the running count number into a “true count”.
We can calculate the true count or count per deck in several different ways, but the easiest method is to divide the running count by the decks remaining in the shoe. If the game is played with a total of 6 decks and we have a running count of 8, after several hands have been dealt, the number of decks in the shoe drops to 4. To find the true count, we simply divide 8 to 4, which is 8/4=2 (+2).
However, sometimes the true count is not a whole number – if we estimate the remaining decks in the same example to be 5, the calculation for the true count will be 8/5=1.6. We can convert it into an integer by rounding up to 2 or rounding down to 1. Most card counters prefer rounding up to the nearest whole number or negative integer – the true count could be negative, as well.
Another important thing is estimating the number of decks, remaining in the shoe. A true estimate is simply impossible – some players would consider the cards seen in the shoe, although it is hard to estimate the number of shoes in there, while others would look at the discard tray to see how many decks have been used and how many are left. No method is absolutely accurate, however.
Players can also try to count the number of cards seen – those on the table plus those in the discard tray, but this is quite difficult for most people, especially while trying to keep a running count during play.
Adjusting Bet Size
Once players estimate the true count and see whether the odds are stacked against them or are in their favor, they can adjust their bets accordingly. If they keep betting the same amount throughout the game, the entire process of counting and estimating the true count is practically useless. When the true count rises, it suggests that the house has lost its advantage and it is time for players to raise their bets.
This is the only way to capitalize on the good odds and on your card counting skills. With most counting systems, it is best to increase the bet size once the count reaches +2 or higher. The exact bet size per hand will, of course, depend on the player’s bankroll and predetermined betting spread. The bet per hand should increase proportionally with the true or running count – for instance, the betting spread is 1-10 and the basic betting unit is $5, the table minimum.
- True count is negative – Do not play the game
- True count is 0 – Bet $5
- True count is 1 – Bet $5
- True count is 2 – Bet $10
- True count is 3 – Bet $15
- True count is 10 – Bet $50
Team play has always been popular among blackjack card counters and it has been portrayed somewhat accurately in several books and movies. The famous story about the MIT Blackjack Team, however, is not very accurate because, throughout the years, there have been multiple blackjack teams that recruited students from the Massachusetts Institute of Technology. Many other groups of card counters have existed, too.
Although many believe that these teams are no longer operational, members of many of the teams still play at casinos. Moreover, it is almost certain that new and more advanced group counting tactics have been developed and that there are counting teams in casinos even today when casinos can easily detect counters.
There are multiple schemes and tactics that allow groups of people to obtain a great advantage over the casino but the most commonly used systems include several “spotters” and at least one “big player”. This type of group play was invented by Al Francesco, who has trained and supported multiple teams over the years.
Spotters
The role of the spotters in a card counting team is essential – they are the ones who actually keep a running count of the tables. Sometimes, the spotters can sit at a table, betting the minimum amount allowed. This way can carefully observe the game and keep a count while not raising suspicion from the casino.
Alternatively, they can stand behind a blackjack table (a practice known as wonging) and observe the cards until the count jumps. This could be risky, however, as blackjack tables usually do not attract spectators – unlike roulette or craps tables, for instance, where you will always find a lot of people who watch the game without actually placing bets.
Once the count rises, the spotter discreetly signals another player who starts betting a lot of money to take advantage of the favorable odds. When the count drops, the spotter notifies the other player that this table is no longer hot.
The Big Player
Usually, a counting team would consist of several spotters and one “big player”. When the spotters see a “hot” table, i.e. a table where the count is high, they signal the main player in the team who is usually the most skilled one. The Big Player should know the perfect strategy and should feel comfortable betting huge amounts of money.
If the count is really high, this player bets the maximum allowed by the casino. If he has only a slight advantage, however, he would spread the bets in accordance with the running count. When the table gets cold, the Big Player either leaves or places smaller bets.
Avoiding Detection
This is the most difficult aspect of card counting in a team – as the practice is strictly forbidden in casinos, all team members should try to remain inconspicuous. There are different things teams can do to avoid detection from using very discreet signals between the group to including additional players. Along with the spotters and the Big Player, some teams have also had back-spotters and “gorilla” players.
The gorilla player is a player who pays attention to the signals from the spotters but rather than keeping a low profile, the gorilla is loud, even extravagant and flashy. His job is to draw attention to himself and away from the team. This player switches between hot tables frequently and places large bets.
Even with additional players and very complex tactics, card counting teams are often detected by casinos since all these strategies have already been described in books and films. Floor managers and security experts usually know how to easily spot card counters and card counting teams. This is why group counting is no longer so popular. It is not advertised publicly and if such teams still exist, they are probably extremely secretive and secluded.
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Additional Factors to Consider
Certain card counting systems such as the Hi-Lo are very simple to learn but in order to apply them quickly and with ease in real-money games, players should practice. They could start with a single deck of cards in order to learn the basics but those who want to try the system on the casino floor would have to be well-prepared. This means being able to follow the system for a long time in multi-deck games, having the proper bankroll, and being able to spread your bets as the true count rises and falls.
Of course, card counters should always look for tables with favorable rules so they can gain as much advantage as possible. But how much is that? This varies significantly from one card counting system to another but in most cases, skilled counters can gain up to 2.5% advantage over the house. In most cases, counters can reach player advantage of around 1% or 1.5%. Before sitting at the blackjack table, they should take several more things into account, namely the importance of deck penetration, the variance in each game, and the theoretical Risk of Ruin and Expected Profit.
Deck Penetration 
Variance 
Expected Profit and Risk of Ruin Deck Penetration
We have already described the term “deck penetration” in this blackjack guide and in short, it refers to the percentage of cards that are dealt from the shoe before the dealer decides to reshuffle. For example, if 39 cards have already been dealt in a single-deck game, then this is penetration of 75%. For most blackjack players, including those who use basic strategy, deck penetration is not really important.
It is essential in card counting, however. When the penetration is deeper, this means that the running or true count will be more accurate – when more cards are dealt, the counter collects more information. Usually, up to 100 or 130 cards are cut off in six-deck blackjack games and it drastically changes the player’s advantage. For instance, the player’s advantage in a six-deck game played with the Hi-Lo and a 1-12 betting spread is around 0.64% when two and a half decks are cut off (130 cards). When the penetration is deeper (around 92%) and only 26 cards are cut off, the advantage jumps to around 1.67%.
Usually, card counters avoid double-deck games if more than one deck is cut off (less than 50% penetration), as well as shoe games played with 4 to 8 decks if more than 2 decks are cut off. A good rule of thumb is to never play on tables with penetration of less than 75% penetration.
Variance
Another important concept card counters should consider when they are at the table is the variance of the game. We can explain it as the “luck factor” – even in games with deep penetration of around 80%, counters cannot predict what cards would be dealt next. The count they keep simply shows whether the shoe is rich in high-value cards or not.
The exact cards that would be in play next will always be controlled by the randomness of the shuffle. The variance simply shows how much the randomness or the luck would affect the advantage we gain through good strategy, deep penetration, card counting, etc. The advantage, as expressed in percentages, is only a theoretical concept and reaching it typically takes thousands of rounds, if not more.
Expected Profit and Risk of Ruin
The expected profit, sometimes called expected value (EV), is one of the first things card counters focus on without necessarily understanding it. The expected value, expectation, or long-term expectation and it expresses the value of each decision in the game. It could be expressed as a percentage or as a fraction and it is used in various casino games, including blackjack, poker, and video poker. The expected value depends on multiple factors such as the penetration, the betting spread, the game rules, the strategy used, as well as the number of hands that are played per hour.
Due to the variance, which is quite high in blackjack, players would typically need hundreds of hours of play to make a good profit. Since the EV changes on every hand, it could be used to make decisions – they would affect the player’s bankroll in the long term, however. For instance, the dealer’s upcard is a 3, while the player holds a 12 – that’s a tough decision for most blackjack players and the right decision is to Hit.
The reason is very simple – based on the probabilities, the EV of Hitting is -23.30%, while Standing offers an EV of -25.20%. Both are negative, which means that the player is more likely to lose with both decisions, but it is better to lose less, especially in the long term when losing less is nearly as equally good for the bankroll as winning.
The other concept players need to understand before they start to play for real money is the so-called Risk of Ruin (ROR) – literally, the risk of losing one’s entire bankroll. In a negative-expectation game such as blackjack, the ROR is always present even when the player uses a good card counting system. Although it cannot be eliminated, however, it could be reduced by increasing the player’s bankroll – not as an amount of money but in terms of a number of betting units.
A good rule of thumb is to start with a bankroll that is at least 200 betting units for a ROR of around 40%. This means that four in every ten players are expected to lose their entire bankrolls. This applies to games with standard rules, a betting spread of 1-12, and a perfectly executed strategy. As you can see, this is a high-risk game and it would be safer to increase the bankroll (or divide it into more betting units) to avoid going broke. The Risk of Ruin would be 20% with a bankroll of 400 units, around 10% with 500 units, and around 1% when the player has 1,000 betting units.
Advantages and Disadvantages of Card Counting
Card counting is the only method for gaining mathematical advantage over the house.
It is difficult to count cards in a real-life situation.
Skilled card counters can make huge profits from blackjack.
Card counting does not work for virtual blackjack in online casinos.
There are many simple systems for counting cards that are easy to learn and implement.
Not all card counters manage to make a living from blackjack.
The different methods are readily available online, in various blackjack books, and guides.
The most efficient counting systems are also the most complex and difficult ones.
Card counting could be applied to all blackjack variations.
Card counting is strictly forbidden in casinos, although it is perfectly legal in most jurisdictions.
Card counting allows deviation from basic strategy when necessary.
Card counters must remain inconspicuous and pretend to be amateurs.
Card counting could be practiced solo or in teams.
Casinos take a wide range of measures to detect card counters. Even suspicion could mean lifelong ban from the casino.