blackjack is a card game that has always been very popular in brick-and-mortar land casinos in places like Las Vegas and Macau.
the reason for its popularity is the strategic nature of card counting and other aspects of the game. While roulette and slots are more luck-based, there is a strategy to winning in blackjack.
it’s a game where more strategic decisions can make the difference between winning and losing, and where technique can lead to victory, so to speak. on this page, we’ll break down the basics of blackjack strategy and card counting to increase your chances of winning, as well as applications you can use in real-world games.
basic rules of blackjack
blackjack is a fairly simple game where you win if the sum of your cards is closer to 21 than the dealer’s, although we explain the rules in detail in Rules and Strategies for Blackjack.
however, this simple game has attracted the attention and study of many people, not just gamblers, but mathematicians, statisticians, and others.
▷Check out the rules and methods of other casino games besides blackjack!
blackjack wins and loses in 4 patterns
blackjack is a one-on-one, head-to-head game between the player and the dealer, no matter how many players are playing around the table.
there are four different patterns of winning and losing in blackjack
| blackjack | if the first two cards dealt total 21, it’s a natural blackjack. if the player makes a natural blackjack, the payout is 1.5x. however, if the dealer hits a blackjack, the player loses the hand, even if it is a blackjack. |
| a number close to 21 | in this case, the payout is 2x, meaning that if you wager $100, you’ll get $200 back. however, a natural blackjack (2 cards) will be lost if 3 or more hands add up to 21. |
| push | if the player and dealer tie, it’s a draw, and your bet is returned. |
| both Bust | if both the player and the dealer bust with a 22 or higher, the player loses. |
the most important of these rules is the “if they both bust, the player loses” rule. on the flip side, you could also say that the player has a better chance of winning if no bust occurs.
special rules that disadvantage the dealer
the word dealer conjures up images of a powerful figure that somehow dominates the game, but in reality, you don’t have to fear that the dealer is strong or has a skill set.
that’s because blackjack has special rules that only apply to the dealer, including the following
- hit until your hand is 17 or better
- stay if your total is 17 or higher
it’s very simple, but it’s a fundamental rule in blackjack strategy. according to the dealer’s special rules, there are only six types of hands: 17, 18, 19, 20, 21, and 22 plus a bust.
for players who can analyze the situation and decide whether to hit when the hand is 16, for example, and for dealers who hit according to the rules, the odds of a dealer’s bust are overwhelmingly high.
blackjack also has strategies
given that “the dealer hits until the hand reaches 17” and “if they bust, the dealer wins”, the only way for a player to win is to “not try to win too hard“.
this means that it is very important to look for two things in the three cards dealt to you: your hand and one card revealed by the dealer.
- the probability that the dealer will bust
- the probability of the player not busting
this is where the strategy of card countingcomes into play. more on this below, but since avoiding a bust (a total of 22 or more) is so important to the player, we can estimate the probability of a bust by counting the cards still in the deck.
since the number of cards used in blackjack is fixed, we can statistically obtain both probabilities, which is why mathematicians and statisticians are interested in studying them, as they can help us improve our chances of winning the game.
basic concepts of blackjack odds/card counting
what makes blackjack so different from other casino games is that it is a game of dependent probabilities.
in a single-deck (1-deck) game, the game continues until all 52 cards have been played, so card counting allows you to make some predictions about what will come next.
▶︎Types of effective system bets
in blackjack, previous game results affect the odds
in games like roulette or poker, the outcome of the previous game does not affect the next game, which is called independence. this is because the deck (one set of cards) is reset each time the game starts, rather than a set deck (one set of cards) like in blackjack, so each game is played under the same conditions.
blackjack, on the other hand, has a set number of decks of cards, and they are dealt in a case called a shoe, and cards drawn once are not put back into the shoe, so cards used in the previous game will not appear in the next game.
for example, if you’ve already had a lot of A’s, J’s, etc. in the previous game, the odds of a natural blackjack are significantly lower in the next game, meaning that the number of blackjack-prone numbers 10, J, Q, Q, K, and A’s in the deck is reduced, which works against you.
this phenomenon of past games affecting future games is known as dependence, and it’s the nature of dependent probabilities and the unique rules that make blackjack a winning game.
basic concepts of card counting
card counting is the art of remembering the numbers of cards dealt in a previous game, which can be briefly explained as follows
- remember the number of cards dealt so far.
- estimate the number of cards remaining in the shoe based on the memorized numbers.
- predict which cards are more likely to be dealt in the context of the cards you predicted.
predicting a card at this stage can lead to two possibilities
you have a lot of large numbers left, from 10 to A
- player Wins Blackjack
- the dealer busts and loses
which makes it easier for the player to win.
if there are a lot of small numbers left from 1 to 3
- blackjack is established
- the dealer busts
these two probabilities are reduced, making it harder for the player to win. as explained above, the dealer’s side has a “hit until the hand is 17 or higher” rule, so if there are a lot of small numbers left, it’s easier for the hand to stay above 17, making it less likely for the player to win.
card Counting Basics: What is the High-Low System?
card counting is a way of remembering the cards from the previous game to predict the next card, but it’s actually quite difficult to remember the cards in detail at a table where there’s a lot of action going on.
that’s why card counting is designed to be applied without having to remember all the numbers. in a high-row system, which is a common method of card counting, the score for count value is
example of calculating a card counting rule in a high-row system
number of cards | count value in a high-low system |
2,3,4,5,6 | 1 |
7,8,9 | 0 |
10,J,Q,K,A | – 1 |
apply this count value to all the cards that have appeared in the game to predict the next card as the sum of the count values.
- player ①: 9・J → -2
- player ②: 2・4・K → 1
- player ③: 4・5・8 → 2
- dealer: 6・3・8 → 2
total count value : -2 1 2 2 2 = 3 (count value is positive)
the count value is calculated based on the number of cards dealt by each player and the dealer to determine whether the total is positive or negative. This high-row system has the advantage of being easy to calculate for beginners because you don’t even need to remember the type of cards dealt.
based on the pattern of positive or negative count totals, you can create the following strategies
if the count value is positive in the high-low system
a higher total count value means that there are more small numbers in the chapter. for example, a total count value of 3 means that there are a lot of small numbers (2-6) and a higher probability of large numbers (10-A).
as a result, if the total count value is positive, the player is in a favorable situation and can decide to play aggressively. however, depending on the player’s or dealer’s hand, it may be more favorable to not draw a card, as shown in the example below.
- if the player’s hand total is 7 4=11 → There is a high probability of a 10 remaining on the shoe, so you can draw a card and try for a blackjack!
- the player’s hand total is 5 10=15 → The player should not draw a card as there is a high probability of a bust on the next hit.
- the dealer’s hand total is predicted to be 12 or higher → The dealer is likely to bust on the next hit, so the player should not draw any cards.
another option is to play it safe and assume that the dealer is likely to bust. it’s also important to note that both the player and the dealer will lose if a bust occurs.
when the count goes negative in a high-low system
if the total count value is negative, you’ve already been dealt a lot of big numbers from 10 to A. there are a lot of small number cards left in the shoe,
- difficult for the dealer to bust
- player’s first hand is likely to be weak
you can think of two cases
a lower probability of the dealer busting naturally means a lower probability of the player winning. in this case, you may need to make a judgment call, such as avoiding aggressive play and waiting for the dealer to bust, or moving the table. basically, if the count value is negative, the odds in the player’s favor are reduced.
running and true counts are important in card counting
in card counting in the high-low system described above, the total count value is also known as the running count because it changes from time to time as the game progresses.
it is also important to judge by the true count when practicing at an online casino. in blackjack, it’s also good to know the true count, as decks are often added to make card-counting strategies more difficult.
blackjack often uses multiple decks
many casinos use multiple decks in the shoe to counteract the running count, making it more unpredictable with the running count than with a single deck.
in multi-deck blackjack, which contains six or eight decks, the total number of cards is higher, making the running count less accurate.
we recommend True Count for multi-deck blackjack
topredict how a multi-deck blackjack hand will play, you’ll want to use a technique called the true count.
this can be calculated by simply dividing the running count by the number of decks remaining in the shoe. For example, if the running count is 4 and the number of decks remaining is 2, the true count is 2.
however, in both the running count and the true count, minus is minus and plus is plus. it’s a way of rescaling the number by the number of decks, so to speak.
if the true count is 1 or higher, the player has an advantage
the effect of utilizing True Count is that you’ll be able to better distinguish between the strength and weakness of your predictions. in general, a true count above 1.0is said to favor the player.
- running count 5, number of decks remaining is 7 → True count = 0.71
- running count 4, number of decks remaining is 4 → True count = 1
- running count 3, number of decks remaining is 2 → True count = 1.5
in the above example, even with the highest running count of 5, the number of decks is still high, resulting in a lower True Count value. conversely, even if the Running Count is as low as 3, the low number of decks remaining will result in a higher True Count, indicating that anything above 1 is a favorable situation for the player.
▷ Practice counting at an online casino!
blackjack card counting techniques by difficulty level!
the basic concept of card counting is easy to understand with the high-low system as introduced above, but keeping a cool head when things get heated in a table game like blackjack can be difficult for inexperienced players.
that’s why card counting has developed a number of different methods, ranging from relatively accessible to beginners to highly technical, depending on the player’s playing experience.
we’ll introduce you to some of them, so you can choose the card counting that suits your play style.
card Counting for Beginners｜Casual System
card counting is a technique that uses the numbers of cards on the field to predict the next card. in the basic high-low system, you count either 1/0/-1 based on the number of cards you’ve seen, but in what’s called the ” casual system ” of card counting, you don’t check the number of cards each time.
instead, you look at the flow of the table as a whole and make judgments based largely on the flow of the scene and nuance, such as ‘I see a lot of small numbers’ or ‘I see a lot of big numbers‘.
it may seem a bit clumsy, but as you continue to play this casual system, you’ll get a feel for the flow of the game, and your chances of winning will surely increase.
if you’re a beginner who finds the high-low system or true counting intimidating, we recommend that you start with the casual system, which is the most basic action in blackjack strategy.
a counting method similar to the Hi-Low System｜K-O System
TheK-O system (Knockout Card Counting System ) is a similar counting method to the Hi-Low system, and counts as shown in the table below. The number 7, which is counted as a 0 in the Hi-Low system, is counted as a 1 in the K-O system.
number on the card | Count value in the K-O system |
2,3,4,5,6,7 | 1 |
8,9 | 0 |
10,J,Q,K,A | – 1 |
blackjack also has clearly defined playing and betting criteria: if the sum of the count values is greater than or equal to 2, aggressive bets should be made; conversely, if the count value is less than -2, players are advised to bet cautiously.
more Advanced Card Counting Techniques｜Red 7 Card Counting System
after understanding the basics of card counting, a more strategic system is the Red 7 Card Counting System.
the counting method for the Red 7 system is basically the same as the Hi-Low system, but with the addition of a score of 1 for a red 7 and 0 for a black 7.
in Red 7, you start with a count value of ‘number of decks × -2’, so for example, if there are 6 decks left in the shoe, it would be 2×-6, starting with a count value of -12.
and the closer the total count value gets to zero, the more it favors the player. the turning point is when the count value reaches zero, which is when it becomes clear that the situation is in the player’s favor and it’s time to aggressively increase the bet amount.
you might be a little puzzled as to why we’re treating the red 7 so specially, but it’s a statistically proven system that you should definitely try out as an application of card counting.
how Much Can Card Counting Increase Your Winning Odds in Blackjack?
we’ve shown you how card counting can be practiced in blackjack, but it’s also worth checking out how much it can improve your odds when practiced at a high-stakes online casino.
typical blackjack RTP at an online casino: 98%
as we mentioned on our page explaining online casino returns, the gambling available at online casino sites tends to be higher than at land-based casinos. in the case of blackjack, this varies depending on the game, but on average, the return to player (payout percentage) is 98%.
of course, 98% is a high return rate, but on the average bet, it falls short of 100%, which means that players tend to lose, which is why card counting is required to increase the return rate of blackjack.
card counting can increase the RTP by 1-3% with card counting
utilizing card counting, such as the Hi-Low system or the Red 7 system described earlier, can increase the payout percentage of blackjack by 1-3%, which can be as high as 99-101% at RTP, making the player more profitable even at average returns.
while a 1-3% increase in win rate may not seem like much to some players, it’s especially important in long-term play. for example, if you bet $10,000 on blackjack in a live game, a 1% difference in odds translates to a $100 difference in profit or loss.
just as slot games also favor models with high payouts and high RTPs, for high rollers who bet for long periods of time or have high single bet amounts, even small increases in win rates and return rates can make a big difference in their expectations and winnings.
is card counting illegal in blackjack?
there’s an American movie called 21, released in 2008, in which a genius college student challenges a Las Vegas casino with a strategy that incorporates counting.
in the movie, you can experience an incredibly high level of card counting, but card counting is not allowed in real land casinos (casino resorts).
card counting is prohibited in land casinos
card counting is prohibited in many land-based casinos due to the high probability of it working in the player’s favor. while it’s not legally prohibited, it’s considered by casinos to be a player-favoring behavior that lacks fairness.
offshore casinos are basically prohibited from taking notes during gameplay, so players are forced to count from their own memory, which can be a huge burden for beginners.
also, if you’re caught card counting in a land-based casino like Las Vegas or Macau, you can expect to be kicked out immediately and, in some cases, even blacklisted and banned.
the best place to utilize card counting is at an online casino!
on the other hand, what about online casinos that you can play on the web? online casinos may also have rules that prohibit card counting.
however, in online casinos, the dealer can’t see you, so it’s impossible to tell if you’re counting cards or not.
plus, online casinos allow you to analyze the table without being present, so you can practice getting used to card counting in blackjack by watching other players’ bets.
however, if you’re practicing card counting at an online casino, you can only do so in a live casino. live casinos are where you play live over the internet with a real dealer, or in other words, remote blackjack. in addition to blackjack, you can also learn how to play baccarat, a popular game among Korean players, at live casinos.
online blackjack that is not a live game may not be able to fulfill the card counting theory because the cards are reset after each game, so it is recommended to choose a live game to practice card counting.
many trusted online casinos have live games going on all the time, so why not try the casual system first? there are also ways to play online casinos for free, so be sure to give them a try.
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