Definition
Card Counting
Also known as Counting Cards, Advantage Play, Hi-Lo
By Abhinav VasudevanReviewed Editorial policy
In short
Card counting tracks the ratio of high to low cards remaining in a blackjack shoe, allowing a player to raise bets when the deck favours them. It is legal, it works, and casinos are entitled to ban you for it.
Card counting is the one widely known method of turning a casino game positive. It does not involve memorising cards, and it does not tell you what will come next.
Why it works
Blackjack is not independent from round to round. The cards dealt are removed from the shoe, so the composition of what remains changes.
A deck rich in tens and aces favours the player, because:
- Blackjacks become more frequent, and they pay 3:2 to you but only 1:1 to the dealer
- The dealer busts more often when forced to draw to 16
- Doubling and splitting succeed more often
- Insurance becomes a positive bet
A deck rich in low cards favours the dealer for the mirror reasons.
The Hi-Lo system
The standard count assigns values:
| Cards | Value |
|---|---|
| 2–6 | +1 |
| 7–9 | 0 |
| 10, J, Q, K, A | −1 |
Add these as cards appear to get the running count. Divide by the estimated decks remaining to get the true count, which is what actually matters. A running count of +6 means very different things with one deck left versus six.
Raise your bet as the true count rises. A true count of +2 is roughly break-even; each point above that is worth about 0.5% of edge.
What it actually earns
A skilled counter playing a good game achieves an edge of 0.5% to 1.5%. That is real, and it is small.
The practical consequences:
- Variance is enormous. Swings of hundreds of betting units are normal. A meaningful bankroll is typically 500 to 1,000 units.
- Bet spread must be wide: often 1:8 or more between minimum and maximum bets, which is exactly what makes counting detectable.
- Hourly returns are modest relative to the capital and the hours required.
Legality and consequences
Counting is legal in almost every jurisdiction. You are thinking, which no law prohibits.
Casinos in most places are nonetheless private businesses entitled to refuse service. In the United States, counters are routinely backed off, barred or entered into shared databases. Atlantic City is a partial exception, where casinos cannot bar counters outright but may restrict their play.
Countermeasures are also now largely automated: continuous shuffling machines eliminate the count entirely, frequent shuffling limits deck penetration, and 6:5 payouts remove enough edge that counting cannot overcome them. Most modern casino floors are structurally count-proof, which is why the practice is far rarer than its cultural profile suggests.
Common questions
Is card counting illegal?
No. It is legal almost everywhere, because you are thinking, which no law prohibits. Casinos are private businesses that can refuse service, and in most of the United States counters are routinely barred or entered into shared databases.
How much does card counting actually earn?
A skilled counter achieves an edge of 0.5% to 1.5%, which is real and small. Variance is enormous, a bankroll of 500 to 1,000 units is typical, and the wide bet spread required is exactly what makes counting detectable.
Does card counting still work?
Rarely on a modern floor. Continuous shuffling machines eliminate the count, frequent shuffling limits deck penetration, and 6:5 payouts remove enough edge that counting cannot overcome them.