Card counting in blackjack means tracking the balance of high and low cards that have already been dealt to estimate the composition of the cards still to come.
You do not need to memorise every card. With the popular Hi-Lo system, you assign cards a value of +1, 0 or -1, maintain a running count, then adjust it for the estimated number of decks remaining.
It sounds simple on paper, but reliably counting while also following blackjack strategy and keeping up with a live game takes considerable practice. It does not guarantee a profit, and gambling always involves the risk of losing money.
What is card counting in blackjack?
Card counting is a way of using information from cards that have already been dealt in blackjack. The principle works because removing different cards from the shoe affects the remaining composition differently.
In general, a greater concentration of tens and aces among the undealt cards can be more favourable to the player, while a greater concentration of low cards tends to favour the dealer.
Counters therefore do not normally try to remember that, for example, the seven of clubs and queen of hearts have appeared. Instead, a counting system reduces the cards to simple numerical values.
Before learning a counting system, it helps to understand how to play blackjack, including hitting, standing, doubling and splitting. Card counting does not replace the underlying rules or basic strategy.
How to count cards in blackjack with Hi-Lo
Hi-Lo is one of the best-known card-counting systems and is a useful example because its arithmetic is straightforward. Each card receives one of three values:
- Cards 2, 3, 4, 5, and 6 have a Hi-Lo value of +1.
- Cards 7, 8 and 9 have a Hi-Lo value of 0.
- Cards 10, Jack, Queen, King and Ace have a Hi-Lo value of -1.
Because a complete deck contains the same number of +1 and -1 tags, Hi-Lo is described as a balanced counting system. If you correctly count through an entire standard deck, your final count should return to zero.
Learning the system can be broken into four basic stages.
Assign a value to every card
Start by learning the three groups until recognising them requires little conscious calculation. For example:
- a 4 adds one to the count;
- an 8 makes no change;
- a king subtracts one.
The suit is irrelevant. A four of hearts and four of clubs both count as +1. This is also why card counting is different from memorising every card that has appeared.
Keep a running count
At the start of a newly shuffled shoe, a Hi-Lo running count begins at zero. Update that total for every exposed card, including cards dealt to other players and the dealer.
- Imagine the following cards appear: 5, King, 2, 8, Ace, 6
- Their Hi-Lo values are: +1, -1, +1, 0, -1, +1
- Starting from zero, the running count changes like this: +1 → 0 → +1 → +1 → 0 → +1
- The final running count is therefore +1.
A positive running count indicates that, relative to low cards, more high cards remain than would otherwise be expected. A negative count indicates the opposite. That does not tell you which card will be dealt next, and it certainly does not guarantee the outcome of the next hand.
Convert the running count into a true count
The running count becomes less informative when several decks are being used.
A running count of +6 with one deck left is very different from +6 with six decks left. In the second situation, the imbalance is spread across many more unseen cards.
Balanced systems such as Hi-Lo therefore use a true count:
True count = running count ÷ estimated decks remaining
Suppose your running count is +8 and you estimate four decks remain:
+8 ÷ 4 = +2 true count
If the running count were +8 with two decks remaining:
+8 ÷ 2 = +4 true count
The difficult part in a real game is not the division itself. You also need to estimate how much of the shoe remains while following the action accurately.
Understand what the count means
A higher positive true count indicates a greater concentration of high cards relative to low cards in the remaining shoe. This matters because high cards can benefit the player in several ways, including increasing the frequency of blackjacks and affecting some doubling and dealer-bust situations.
A negative count indicates a less favourable remaining composition.
However, knowing the count is only one component of advantage play. Rules, the number of decks, how deeply cards are dealt before a shuffle and accurate playing decisions can all affect the mathematics.
Card counting should therefore not be treated as a formula for guaranteed winnings.
Running count vs true count
These two terms are easy to confuse.
The running count tells you the raw imbalance you have observed.
The true count puts that number into the context of how many cards remain. This is particularly important in multi-deck blackjack.
For example, a +4 running count with half a deck left represents a much greater concentration of extra high cards than the same +4 with several decks still in the shoe.
How to practise card counting
A sensible way to learn the mechanics is away from gambling altogether, using an ordinary deck of cards. There is no need to risk money while learning.
Start with a shuffled 52-card deck and turn over one card at a time. Add +1 for cards from 2 to 6, ignore 7 to 9, and subtract one for tens through aces.
Your final count should be zero.
Once you can do that accurately, try recognising pairs of cards. A low and high card cancel each other out, so combinations such as a 5 and queen equal zero.
Only after the running count becomes comfortable does it make sense to practise estimating decks and calculating a true count.
Accuracy matters more than speed. A counting error can carry through the remainder of the shoe and make subsequent calculations unreliable.
A blackjack trainer can also help with the separate task of learning basic playing decisions. Counting accurately is of limited value if you are simultaneously making avoidable strategy errors.
Does card counting guarantee you will win?
No.
Even when the remaining shoe is favourable, an individual hand is still uncertain. You can receive a poor hand during a positive count or win during a negative one.
Card counting concerns changing probabilities over a sequence of hands, not predicting the next card with certainty.
That distinction is important. Short-term results can vary substantially, and a player can lose money even when making mathematically informed decisions.
Claims that a counting system guarantees winnings or removes the risk from blackjack should therefore be treated sceptically. Blackjack remains gambling, and money put at risk can be lost.
Is card counting illegal in the UK?
There is an important distinction between mentally keeping track of exposed cards and cheating or interfering with a game.
As of August 2026, section 42 of the Gambling Act 2005 creates an offence of cheating at gambling, including conduct intended to enable or assist another person to cheat. The legislation also refers to actual or attempted deception or interference with the gambling process as possible forms of cheating.
The Act does not simply state that mentally maintaining a Hi-Lo count is itself a criminal offence. However, that should not be interpreted as permission to use prohibited equipment, interfere with a game, deceive casino staff or breach other applicable rules.
A casino can also have its own conditions and policies. If venue staff tell you to stop playing or leave, comply with their instructions.
For anyone interested in the distinction between legitimate strategy and prohibited behaviour, it is worth understanding that attempts to cheat at blackjack are a different subject from mentally tracking cards that have been openly dealt.
Can you count cards in online blackjack?
It depends on how the game operates, but card counting often has little or no practical application to online blackjack.
Many digital blackjack games use software-generated outcomes and may effectively reshuffle between hands or use game mechanics that prevent a useful count from carrying forward.
If previous cards have no meaningful effect on the composition available for the next round, maintaining a running count provides no useful information.
Live-dealer blackjack can involve physical cards, but the usefulness of counting still depends on factors such as the number of decks and when the shoe is shuffled. Rules and procedures vary between games.
Check the specific game's rules rather than assuming a method developed for a traditional shoe game will transfer directly to an online version.
Card counting and basic blackjack strategy are not the same
Card counting and basic strategy solve different problems.
Basic blackjack strategy considers your hand, the dealer's visible card and the game's rules to determine a mathematically informed playing decision.
Card counting tracks the changing composition of undealt cards.
Someone learning blackjack should generally understand basic strategy before attempting to maintain a count.
Our guide to blackjack strategies provides more context on the different approaches players use.
More advanced counters may study "strategy deviations", where particular decisions can change according to the true count. These require considerably more study than the basic Hi-Lo running count and should not be confused with a guaranteed way to win.
Common card-counting mistakes
The arithmetic involved in Hi-Lo is basic, but applying it consistently is harder. Common problems include:
- Missing cards: every exposed relevant card needs to be incorporated into the running count.
- Forgetting the count: distractions can cause the current total to be lost.
- Confusing running and true counts: a positive running count is not equivalent to the same true count.
- Estimating decks badly: an inaccurate estimate affects the true-count calculation.
- Ignoring basic strategy: counting does not substitute for knowing how the underlying game works.
- Assuming a positive count guarantees a win: it changes the composition and associated probabilities; it does not determine the next hand.
- Trying to count unsuitable games: frequent shuffling can remove the information a counter is trying to use.
These are among the reasons that understanding Hi-Lo takes far less time than applying it reliably.
Other blackjack counting systems
Hi-Lo is not the only method. Other systems include KO (Knock-Out), Hi-Opt and more complicated multi-level counts.
Some systems assign different values to additional cards, while unbalanced systems such as KO are constructed so that a complete deck does not necessarily finish at zero.
Greater complexity is not automatically better for an individual player. A theoretically more precise system offers little benefit if the extra mental workload causes counting errors.
For somebody simply trying to understand how to count cards in blackjack, Hi-Lo provides the clearest introduction to the underlying principle.
Play with limits, not expectations of profit
Learning the mathematics behind blackjack can be interesting, but gambling should be treated as paid entertainment rather than an income source.
Decide beforehand how much money and time you are prepared to spend, and never chase losses or increase stakes because you feel you need to recover money. A counting system does not eliminate financial risk.
If gambling is becoming difficult to control, free confidential support is available. As of August 2026, GamCare states that the National Gambling Helpline is available 24 hours a day, every day of the year, on 0808 8020 133, with online support also available.
FAQs
Is it hard to learn how to count cards in blackjack?
The basic Hi-Lo arithmetic is straightforward: add one, subtract one or make no change. The difficult part is keeping an accurate running count, estimating the decks remaining, calculating the true count and following the game simultaneously.
Do you have to memorise every card?
No. Hi-Lo groups cards into three categories and maintains a numerical total. You do not need to remember every individual card and suit.
What does a positive count mean?
In Hi-Lo, a positive count means proportionally more high cards remain than low cards compared with the starting composition. In a multi-deck game, the running count needs to be considered alongside the estimated decks remaining.
What is the easiest way to practise counting cards?
Practise with a normal deck without gambling. Turn over cards one by one, assign their Hi-Lo values and keep a running total. Because Hi-Lo is balanced, a correctly counted complete deck finishes at zero.
Can card counting predict the next blackjack card?
No. Counting provides information about the composition of the remaining cards; it does not tell you exactly which card will appear next.
Does card counting always work?
No. Its usefulness depends on the game structure, rules and shuffle procedure, and accurate counting still cannot guarantee winning hands or a profit.
