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A Detailed Introduction to Blackjack Strategy: Card Counting

It’s the most famous casino strategy in the world, inspiring Hollywood movies and endless misconceptions: blackjack card counting.

If you’re an aspiring or experienced blackjack player wondering how to count cards in blackjack, with multiple decks or just one, here’s your answer.

But very quickly, why does card counting even exist? The fact is that by using perfect basic strategy (the optimal per-hand play for blackjack) players reduce the house edge to 0.5%. That’s good, but the casino still wins. The addition of counting can bring house edge as low as -1.0% or beyond – a mathematical advantage for the player.

Blackjack Card counting strategy - blackjackcanada

So what is card counting, exactly?

Card counting is a technique player use to track which cards have not yet been dealt at the blackjack table. This allows players to predict when the odds of winning are highest (or lowest) and adjust their bets accordingly. When win odds are high, players will increase their wagers.

Once the count (and therefore the advantage) drops, players resume their lower-stakes betting.

Is counting cards illegal?

The odds of winning at blackjack by counting cards are very high – but it’s still perfectly legal. Perhaps this is because many players try to count without adequate practice, fail, and the casino profits anyway. While not illegal, many casinos will force players to leave if they’re caught counting successfully.

Card counting strategy: the basic idea

We’ll dive into specific strategies next, but for anyone that’s new to counting, here’s a quick idea of how it works. We start by assigning every card in the deck a value. Typically:

  • 2-6 are plus 1
  • 7-9 are zero
  • 10- ace are minus 1

The count starts at 0 before any cards are dealt. Every time a card is shown, you add 1, subtract 1, or do nothing. So if the first three cards dealt are 10-Q-8, then the count is +2. This is called the running count and accurately keeping the count is at the core of the strategy.

We want the count to be as high as possible since this means there is a larger proportion of high-value cards in the deck, which benefits the player. A low count (i.e. more low-value cards in the deck) benefits the dealer. When the count is sufficiently high, it’s time to raise the stakes.

Why is a high count beneficial?

Let’s look at some blackjack fundamentals. Imagine in a single-deck game, the first 10 cards dealt are all low-value, between 2 and 6. The player’s odds of being dealt 20 or 21 have increased significantly since there are now proportionally more 10s available. If dealt a lower hand (say 14) players know the chance of then drawing a 10 (and going bust) is higher, so they might stand here.

But the dealer must hit on anything less than 16, so a high count means they’re far more likely to go bust. This propensity to bust is what can tip the house edge from +0.5% to -1.0% or further.

Specific and popular card counting strategies


This is the strategy we’ve just examined: low cards are +1, high cards are -1, everything else is 0.

It’s by far the most popular and historically successful strategy in blackjack. It takes training and practice to do the real-time arithmetic, but it doesn’t take a genius to nail Hi-Lo. Just remember that how to count cards in blackjack with multiple decks is slightly different: it’s necessary to divide the running count by the number of decks to calculate the true count.

We use the true count to make your decisions.

Wong Halves

The Wong Halves method is a significant step up in sophistication (by introducing fractions and more groupings) for a minor gain in effectiveness over Hi-Lo. However, blackjack is a game of minor gains, and if executed perfectly, players will win more using this method.

  • -1 for 10, ace and face cards
  • -0.5 for 9
  • 0 for 8
  • +0.5 for 2 and 7
  • +1 for 3, 4 and 6
  • +1.5 for 5

The betting approach (increase wager for high counts) is unchanged compared to Hi-Lo.

Omega II

Omega II is also slightly more effective than Hi-Lo, but not as powerful as Wong Halves despite its increased complexity.

  • -2 for 10 and all face cards
  • -1 for 9
  • 0 for 8 and aces
  • +1 for 2, 3 or 7
  • +2 for 4, 5 and 6

Factors to consider when counting cards online

  • Basic strategy – There’s no benefit to learning card counting if players don’t have a basic strategy (the optimal method for playing every hand in blackjack) nailed down. First strategy, then counting.
  • Type of game – You ideally want to play single-deck blackjack with dealers hitting on soft 17. No funky rules or interpretations, and remember to only play live dealer games if you’re counting online. RNG games are 0% susceptible to counting since all decks are instantly shuffled after each hand.
  • Number of decks – The number of decks isn’t too important, just note how many there are so you can find the true count. In addition, if a table uses Continuous Shuffling Machines (CSMs) then leave, as it makes counting cards impossible.
  • Playing in groups – Counting with 1, 2, or 3 others has been shown to cut the house edge to as little as -4%, but it is tricky. Try it out with some friends.
  • Use of side bets – There are counting strategies for maximising side bets, but for most regular gameplay be sure to ignore all side bets: they only serve to increase the house edge.

Blackjack card counting FAQs

Card counting is not explicitly cheating - it’s just a superior playing strategy. It’s also hard for most people to master, so poses limited risk to casinos.
They do exist, but of course it’s much faster to apply it yourself at the table. And if you’re at a land-based casino, all apps/devices are strictly banned.
Card counting is an extra skill set applied in addition to perfect strategy.
With a few months of dedicated effort, anyone can become proficient at counting.