How to Count Cards in Blackjack – A Complete Guide to Beating the Game

Count cards in blackjack

There are many myths about card counting that portray the strategy as a near impossible task for the average Joe. Movies such as Rain Man and 21 pretty much tells us that you have to be a genius to count cards and that any game using six or eight decks can’t be beaten. Well, none of this could be further from the truth.

Card counting is actually pretty easy and anyone that can focus on a task and quickly use addition and subtraction can master it. Making a living out of card counting is much more difficult though, but this has little to do with intellect and more about patience and bankroll size.

If you want to learn how to count cards, we have covered everything you need to know in the following guide. Read this through and you will soon master the art of card counting, which allows you to beat blackjack and guarantee yourself a long term profit from the game.

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Understanding the basics of card counting

You may already know that blackjack is a highly mathematical game that is all about probability. The decisions that you make can be more or less advantageous to you depending on the unique situation that you’re in – what cards you have been dealt and what card the dealer is showing.  

To little surprise card counting is also all about probability.

To understand this in its simplest form let us say that you have a bucket of 10 black balls and 10 white ones in front you. Picking a white ball will earn you a prize while a black one is a loss. On your first pick I think we can agree that your probability of picking a white or black ball is 50% as there’s an equal amount of them.

But what about the second pick? If you chose a white ball on your first, would you be as likely to pick another white and win the second time around? Of course not; your chances would be lower as there are now more black balls than white ones. The opposite also applies if you picked a black ball on your first try. Your chances of winning on the second round would then be higher.

But blackjack isn’t about picking balls, is it?

Well, as a matter of fact the white balls could actually be converted into tens, jacks, queens, kings and aces, while the black ones could be converted into 2s, 3s, 4s, 5s and 6s.

You see, the tens, face cards and aces are the types of cards that are advantageous to us players. The more of them there are the more likely we will be to win. The same logic goes with the low valued cards, which are bad for us and good for the house. The more of these there are the less likely it is that we will beat the dealer.

But the quantity of a certain card doesn’t change, does it?

Unless you’re playing a virtual blackjack game against the computer it does. In real casinos and live casino games the decks aren’t shuffled between hands. Thus the ratio of high valued cards (aces, tens and face cards) and low valued ones (2 – 6) is constantly shifting from one game round to another. This is how you can use card counting to gain an advantage in the game and actually beat it.

When the ratio of high to low valued cards is high enough, the RTP (your long term theoretical return) will be boosted to more than 100%, guaranteeing you a profit in the long run. Sounds good doesn’t it? Now let’s take a closer look at how the RTP is increased or decreased by different cards that are dealt in the game.

The efficiency of card counting

Before explaining the practical method of counting cards, let us take a look at the efficiency of it. Understanding this will be crucial to how you use the card counting strategy and to the long term results that it will yield you.

Whenever blackjack is played with a single deck of 52 cards, the RTP of the game will be affected in the following ways when a specific card is dealt (thus removed from the deck):

Change in RTP when a card is removed (dealt)
Card
2
3
4
5
6
7
8
9
10
A
RTP
+0.38%
+0.44%
+0.56%
+0.71%
+0.41%
+0.29%
+0.01%
-0.17%
-0.51%
-0.59%

Please note that the above values are based on computer simulations that have been run on perfectly played blackjack using basic strategy where the table rules were S17, double on any cards, no double after split and where pairs could be split up to four hands. Different rule settings may affect the true value of the RTP. However, you don’t have to think about this as the difference is negligible. Please also note that 10 is considered to be all cards that are valued 10, including jacks, queens and kings. 

As you can see in the table, the removal of an 8 makes almost no difference at all, while a removal of a 4 or 5 has a substantial positive impact on the game’s RTP. Furthermore, a removal of a 10, face card or ace has a strong negative effect on your expected return. 

Now let us imagine that a hand were played where you were dealt a 7 and two 5s and the dealer busted with a 7, 6 and a 10. The RTP for the next game round would then have changed as follows:

  • Two 7s removed = +0.58% (2 * 0.29%)
  • One 6 removed = +0.41%
  • Two 5s removed = +1.42% (2 * 0.71%)
  • One 10 removed = -0.51%

All in all the RTP for the second hand would have increased by 1.9%, which is massive considering the fact that perfectly played blackjack already has an RTP of about 99.50%. Thus, if the next hand were to be played correctly this would be guaranteed to yield a profit in the long run. The RTP would be more than 100%.

However, in reality the change in RTP is much lower than described.

This is because real blackjack games are rarely played with a single deck. At internet casinos the tables found in the live casino section are almost always using 8 decks. This will make a huge difference in RTP on the removal of a single card. The impact will be much lower compared to a table using only one deck.

You’re asking why? It’s basic probability.

Let’s think about our white and black ball example again. Now imagine if the total pool of balls were 200 instead of 20. Removing a single ball would just be 1 out of 200, which is 0.5% as opposed to 1 out of 20, which is 5%. It’s a tenfold difference.

The same logic applies to the removal of cards in blackjack. If 8 decks are used a total of 416 cards are in play compared to 52 cards used with a single deck. Removing one card from the 8 decks is 0.24%, while removing one card from a single deck is 1.9%.

Will multiple decks affect the card counting strategy?

It will, of course. It would be much easier to count cards and to gain an advantage if only one deck was used. However, it’s still possible to do it with 8 decks and it’s still not very difficult. Let’s have a look at how it’s done!

This is how you count cards

To make card counting as easy as possible, a strategy known as Hi-Lo has been invented. The method of this strategy is tagging all low valued cards (2s – 6s) that appear with +1 and all high valued cards (10s, face cards and aces) with -1, and getting a total by using addition and subtraction. The 7s, 8s and 9s are considered to have little impact so to make the counting effortless these are not counted.  

Now let us go back to the example that we took earlier where you were dealt a 7 and two 5s and the dealer busted with a 7, 6 and a 10. Here we have two cards that aren’t counted (the 7s); three cards tagged as +1 (the two 5s and the 6); and one card tagged as -1 (the 10). This means that your total count after this game round would be +2 ((3 * +1) – (1 * -1)).

To further understand the counting, let’s illustrate it with a game round where a total of 20 cards are dealt and see how the count changes with each card. This example is very representative of how a single game round could look like if five people were sitting down at a table played with only 1 deck.

Example of card counting in a game round with a single deck in play
Order
Card dealt
Tag
Total count
1st
2
+1
+1
2nd
6
+1
+2
3rd
8
0
+2
4th
4
+1
+3
5th
10
-1
+2
6th
A
-1
+1
7th
10
-1
0
8th
J
-1
-1
9th
Q
-1
-2
10th
4
+1
-1
11th
A
-1
-2
12th
5
+1
-1
13th
6
+1
0
14th
9
0
0
15th
4
+1
+1
16th
4
+1
+2
17th
3
+1
+3
18th
7
0
+3
19th
8
0
+3
20th
2
+1
+4

As you can see, by the end of this game round your total count would be +4. Now how does this impact the next hand that you’re dealt? Well, each count is equal to about 0.50% in RTP. Some cards are of course worth more and some less, but the average is about 0.50%.

This means that with a count of +4 your RTP is increased by 2%. Should you have ended up with a count of -4 instead, your RTP would be decreased by 2%. Here’s another illustration of it:

Count
-4
-3
-2
-1
0
+1
+2
+3
+4
RTP
-2%
-1.5%
-1%
-0.5%
unaffected
+0.5%
+1%
+1.5%
+2%

If you’re playing blackjack perfectly using basic strategy you can easily find blackjack tables that have an RTP of 99.50%. This means that with a count of +1 you would break even and with any count above that you would be guaranteed to make a profit in the long run. It looks easy doesn’t it?

It isn’t quite as easy as it looks though.

So far we have only illustrated how the card counting works when you’re playing at a table that’s only using a single deck. As already mentioned, this is rarely the case – especially not when you’re playing online. Therefore we have to adapt the strategy to multiple decks and learn about something known as true count.  

The importance of true count

The true count is your actual count, or to put it in other words, the true representation of RTP change when playing at a blackjack table that is using two or more decks. As we’ve already covered earlier, there’s a big difference in removing a single card from a pool of 52 (1 deck) and removing a single card from a pool of 416 (8 decks – very common online).

Calculating the true count is not difficult. All you have to do is to divide your current count with the number of decks that are still unseen. In other words, the cards that haven’t been dealt yet.

Imagine playing at a table using 8 decks. At the very beginning of this session (when the cards have just been shuffled) your true count would be your current count divided by 8. Simply because no cards or almost no cards have been dealt yet.

However, after playing for 20 minutes or so we’ve probably used up a good two decks. Thus, there would only be 6 decks left in the shoe – cards that are still unseen. Your true count would now be calculated by dividing your current count with 6. Here’s a table to illustrate it even further:

Example of true count in an 8 deck game
Game roundCountDecks unseenMathTrue count
1
+4
8
4 / 8
+0.5
5
+8
8
8 / 8
+1
10
-7
7
-7 / 7
-1
15
-14
7
-14 / 7
-2
20
+3
6
3 / 6
+0.5
25
+12
6
12 / 6
+2
30
-10
5
-10 / 5
-2
35
-20
5
-20 / 5
-4
40
+10
4
10 / 4
+2.5
50
+16
4
16 /4
+4

You may be wondering how in the world you are supposed to know how many decks are still unseen? It’s all about making an estimation. On the blackjack tables you will find the unseen cards in a shoe and all of the used ones piled up next to the dealer on the opposite side of the table. Use your best judgment to determine how many decks are still unseen. It’s not the end of the world if you’re a little bit off, but you don’t want to be completely off track.

Now that you know how card counting is done, let’s have a look at different betting patterns that you might want to use to make a good profit out of the strategy.

How to bet when counting cards

There are two ways that you can ensure yourself a long term profit by counting cards:

  1. Only play a hand when the true count is high and you know that you’ve got the edge

  2. Bet low when the true count is low and bet high when the true count is high

Using alternative one can be very efficient at online casinos, but it can also make the gameplay tedious as you’ll be sitting out just waiting whenever the true card count is low. Alternative two is another option and at real casinos this is usually the only option as otherwise you could easily be spotted as a card counter and very well be thrown out.

When using alternative two, there is a betting technique known as Kelley Criterion, which focuses on maximizing profits while minimizing the risks of going broke. This technique is simply the following betting pattern:

True count
Units
Real money example 1
Real money example 2
0 or negative
1
£1
£10
+1
1
£1
£10
+2
2
£2
£20
+3
4
£4
£40
+4
8
£8
£80
+5 or higher
12
£12
£120

So what are you looking at here? First of all, a unit is the amount that you start betting with when your true count is zero. If you’re sitting down at a table where the decks were just shuffled and you place a bet of £10 then this is one unit.

You do of course decide yourself how much a unit should be. This is wise to base on your total bankroll and could be anything from the minimum stake at the table to a very high amount. We’ll cover this more thoroughly shortly.

No matter what the value of the unit is, the betting technique tells you to double this whenever your true count is +2 and to quadruple it whenever your true count is +3. Furthermore, at a true count of +4 and +5 or higher you should bet 8 and 12 times more than your intial stake.

It is of course not necessary to follow this particular technique, though it is highly recommended.

Deciding what a unit should be

Even if you’re playing blackjack with an edge that is guaranteed to earn you a profit in the long run, it is very important to understand that short-term results can vary widely. The edge is small and volatility can play a huge role in blackjack. You could be playing for days or even weeks with a positive RTP and still end up losing. That’s the way of the game.

Therefore your bankroll has to be able to handle these downswings, which of course in the long run will turn and eventually yield a profit. You may be lucky to never experience these downswings, but you certainly have to be prepared for them if you’re going to take your blackjack gaming seriously.

Professional blackjack players use a term known as risk of ruin when deciding what their unit should be. This is a value that tells them the percentual risk of losing their entire bankroll. Most players are comfortable with this risk being around 5%. A lower risk means lesser profits.

While we won’t go into details explaining how risk of ruin is calculated, you should know that a 5% risk is equal to a bankroll of about 1000 units. So if you want to make money out of blackjack playing professionally, what you need to ask yourself is how high your total life-time budget is?

Example of units with a 5% risk of ruin
Total budget
Unit (budget / 1000)
£100
£0.1
£1,000
£1
£10,000
£10
£100,000
£100

If the answer to the question is £1,000 (which is a fair starting budget for most semi-serious players), a unit would be equal to £1. Thus, if you’re using the Kelley Criterion betting technique, the betting span would be £1 – £12 depending on the true count.

Changes to basic strategy

To make card counting profitable you should always use basic strategy to maximize the RTP of the table you’re sitting at. If you don’t it is very likely that you’ll take decisions that you shouldn’t which means that you won’t be getting an edge over the casino no matter how high of a true count you get.

However, how you should play according to basic strategy actually changes when you’re counting cards. For instance, taking insurance is never recommended in basic strategy. But if you know that a lot of tens and face cards are left unseen in the shoe it does become a profitable alternative.

If you want to play optimally when counting cards, these are all of the changes to basic strategy that you should know about and follow:

Your hand
Dealer's hand
True count
Decision
16
9
+5 or higher
Stand
16
10
0 or higher
Stand
15
10
+4 or higher
Stand
13
2
-1 or higher
Stand
13
3
-2 or higher
Stand
12
2
+4 or higher
Stand
12
3
+2 or higher
Stand
12
4
0 or higher
Stand
12
5
-1 or higher
Stand
12
6
-1 (in S17) or higher
Stand
12
6
-3 (in H17) or higher
Stand
11
A
+1 (in S17) or higher
Double Down
11
A
-1 (in H17) or higher
Double Down
10
10
+4 or higher
Double Down
10
A
+4 (in S17) or higher
Double Down
10
A
+3 (in H17) or higher
Double Down
9
2
+1 or higher
Double Down
9
7
+4 or higher
Double Down
10 - 10
5
+5 or higher
Split
10 - 10
6
+5 or higher
Split
Insurance or even money
#colspan#
+3 or higher
Take it

To briefly explain the logic behind these changes, let us assume that you’re dealt a jack and a 6 to get a value of 16 while the dealer shows a 9. Here basic strategy says hit as you need 17 or better for a stand to be worth it. However, when there are many tens, face cards and aces left (when your true count is +5 or higher), it is actually better to stand as your risk of busting is heavily increased.  

Making card counting a living

Correct us if we’re wrong to say that it’s every casino enthusiasts dream to make gambling their living. How great wouldn’t it be starting off the day with a cup of coffee and an hour of blackjack knowing that this would pay the bills? So is it doable? Of course, plenty of people have made a fortune as professional blackjack players.

But it certainly isn’t an easy job.

Going back to our section about bankroll requirements and deciding a unit, we mentioned that a bankroll of £1,000 would be the maximum amount that most people would be down investing. So how far would this get you in terms of daily profits?

At most blackjack tables you’ll be averaging 60 – 80 hands an hour. If you want to keep your risk of losing your bankroll low (to 5%) a budget of £1,000 would mean an initial stake of £1 and a stake of £12 whenever your true count is +5 or higher.

If we for a second imagine that you only were to play when your count is +5 (which you wouldn’t) and you played perfectly using basic strategy, your RTP would be 102%. Thus, from every hand you are betting £12 you would be expected to win £12.24 (1.02 * £12) – that’s a £0.24 profit.

With 60 – 80 hands played an hour the hourly profit would be £14.4 – £19.2 and if you played eight hours a day this would equal to a daily profit of £115.2 – £153.6. That is not bad at all. Most of us could make that work for sure.

However, in reality you won’t be playing 60 – 80 hands with a true count of +5 unless you strategize with a group of people. On average half of the hands will be with a negative count and among those that are positive the vast majority will be with a lower stake and a lower return.

So in reality the daily estimated profits would perhaps be a tenth of those described. This means that the budget would have to be ten times as high if you would like to earn £14 – £19 an hour playing blackjack with a low risk. In other words, you would need a budget of £10,000.

This is a lot of money. And one should also know that it might not be half as fun to count cards and play blackjack all day as it may sound at first glance. Thus you would probably want to make a lot more money than £14 – £19 an hour if it were to be worth your while.

Understanding deck penetration

When professional blackjack players pick their tables to play at, one of the most important things that they look for is deck penetration. This is the number of cards that are dealt from a single or several decks before a re-shuffle occurs. The more cards that are dealt, the deeper the penetration is and the deeper the penetration is, the better it is for the card counter.

So why is a deep penetration important?

  • A deeper penetration will make the count range wider as the fewer cards that are left unseen the bigger the difference each dealt card will make. Thus, more favorable opportunities will present themselves with a deeper penetration.
  • A high card count rarely happens in the beginning. A true count of +8 is more or less impossible to get unless you’re at the end of a shoe.

To give you an example of how big of an impact deck penetration actually makes, we can mention a computer simulation that simulated a table using six decks. The computer was using the Hi-Lo card counting strategy with optimal plays from basic strategy and the changes to it, as well as a 1 – 12 unit betting range (the Kelley Criterion technique). Here are the results:

Penetration
Penetration %
Hourly win
Win increase %
4 decks
66%
£12.56
-
4.5 decks
75%
£20.64
63%
5 decks
83%
£34.64
176%

As you can see, there’s a huge difference between the shuffling taking place when 4 out of 6 decks have been dealt and waiting to shuffle until 5 decks have been played through.

Some card counters argue that it isn’t the worth the time counting cards unless the deck penetration is at least the following:

Number of decks used
Penetration
Penetration %
2
1 deck
50+
6
4.5 decks
75+
8
6.5 decks
80%

We wouldn’t take this to heart though, but we would recommend that you make up your own mind about the conditions that are required for card counting to be worth your while.

Playing live dealer games using internet casinos the blackjack tables almost always use 8 decks with a 50% penetration. In other words, not the best conditions.

The legality of card counting

The vast majority of inexperienced players believe that card counting is illegal, which is understandable. If we haven’t heard stories about players being banned from casinos in Las Vegas, we have at least seen films where blackjack players get thrown out of venues for counting cards.

But is it really illegal? Not at all. There is no law that says that using your brain to get an advantage in a casino game is a criminal offence. Not in the UK, not in the US and probably not in any other country either. 

It is, however, frowned upon by casinos and if they want to throw out a player or even ban one they have every right to do so. Now who would have guessed that casinos don’t like players beating them and taking their money? Of course they are going to take action.

Tips and tricks

To finish of the article, here are some valuable tips and tricks on how you can make card counting profitable. Some of them are revisits that we’ve already mentioned in the guide and some are new.

– Use basic strategy

Counting cards is just the icing on the cake that will tip the edge of the game in your favor. For this to work the foundation has to be there. The foundation is playing perfectly by using basic strategy. Preferably you want to apply all of the changes that affect basic strategy when you count cards, which we discussed earlier in the article.

– Use bonus offers

Whether you’re playing offline or online, promotional offers is a way to further increase your chances of winning from blackjack. If you deposit £100 to get an additional £100 to play with this will obviously give you an added value no matter how high the wagering requirement may be.

– Play together in a group

There are definitely advantages to counting cards as a group as opposed to doing it solo. You could all play on your own table and whenever the count gets high you tell your friends to come and play. This way you don’t have to spend a ton of time at a table that isn’t yielding any profit. It will be much easier finding the profitable situations – the bigger the group the more efficient of course.

If you’re playing online and struggling with the card counting (not keeping up with the additions and subtractions), you could also split the counting between you and a friend. You could be counting all of the high valued cards and your friend all of the low valued ones. Then at the end of each game round you would simply add your counts together.

– Don’t over bet

When you know that you’re beating the house it can be easy to become overconfident. However, no matter how high your true count is your edge actually isn’t that good. You could still lose just as much as you can win big in a game where the odds are very much against you. Therefore you have to be careful about your bet amount. If you bet too much and lose you might be spending all of your bankroll even if you were guaranteed to win the long run.

– Play heads-up with the dealer

While this isn’t necessary it’s optimal for you to play alone with the dealer – for two reasons. You will first of all be able to play a lot more hands every hour as each game round will be quicker. Secondly, when you reach a point where your true count is high you want to keep it high as long as possible and not dilute it with other players around. You want to be dealt the high cards that the deck is now rich in as these will give you an advantage. You don’t want other players to be getting them.

Frequently asked questions

Can I use card counting on virtual blackjack games?

Not as far as we know. In these games only one deck is used and this is shuffled between game rounds which makes card counting impossible. However, should you find a game where the deck isn’t shuffled it would indeed be possible.  

Can I make a living counting cards online?

You can, however, if you want to do it safely it requires a big bankroll and a lot of passion. It is not an easy job, but if you do put your mind to it you could indeed make enough money from counting cards and playing blackjack online to sustain yourself.

Will I win more hands at a high true count?

Yes, but it will not be a huge difference. The advantage of a deck rich in tens, face cards and aces come from a higher probability of getting blackjack, as well as being more successful with your double downs and pair splits.

How big must by bankroll be?

It depends on the risk you’re willing to take of losing it as no matter if you’re playing with an edge there will always be a risk of losing your bankroll due to volatility (fluctuations in the game). A good rule is having a bankroll of 1000 times the amount you’re willing to start betting. The risk of losing will then only be approximately 5%. So if you want to play blackjack at an initial stake of £1, you would need a bankroll of £1,000 to be on the safe side.   

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