What is card counting?

Q: What is card counting?

Card counting is a technique that tracks the ratio of high cards (10s and Aces) to low cards remaining in the shoe. When high cards are plentiful, the player has an edge — blackjacks are more common and dealers bust more often. Counters raise their bets when the count is favorable.

The one-line definition

Card counting is tracking the ratio of high cards (10s and Aces) to low cards (2–6) left in the shoe, and betting more when the ratio favours the player. It's not memorising every card dealt — that's a Hollywood myth. It's a running arithmetic tally that anyone can learn in a weekend.

Why counting works at all

Blackjack is the only major casino game where past hands affect future hands. Cards leave the shoe as they're played, so what remains isn't a random sample of a fresh deck — it's a specific subset with a specific composition. When that subset has more tens and Aces than average, two things happen:

You get more blackjacks. More Aces + more tens = more two-card 21s, and those pay 3:2. This is where the bulk of a counter's edge comes from.
The dealer busts more often. With more tens waiting to fall, the dealer's stiff hands (12–16) turn into busts more often.

Together, when the shoe is ten-rich, the house edge flips from about +0.5% for the house to as much as +1% to +2% for the player. A counter doesn't win every hand — nobody does — but they bet big when they have the edge and bet small when they don't, and that ratio is the whole game.

The Hi-Lo system — the standard beginner count

Nearly every serious counter starts with Hi-Lo. Every card has a value:

Card	Count value
2, 3, 4, 5, 6	+1
7, 8, 9	0
10, J, Q, K, A	−1

As cards are dealt — yours, other players', the dealer's — you add or subtract. That total is the running count (RC). A fresh shoe starts at 0. If the RC climbs to +8, that means eight more low cards have been dealt than high cards, so the rest of the shoe is ten-rich in your favour.

From running count to true count

The running count alone doesn't tell you how strong your edge is. A +8 with one deck left is a very different situation from a +8 with six decks left. So counters convert:

True count (TC) = Running count ÷ decks remaining

Eyeball the discard tray or the shoe. Six decks in play, you've seen roughly two decks so far, so about four decks remain. RC +8 ÷ 4 decks = TC +2.

The true count is what you actually act on. Rough guide, per unit of TC, you gain about 0.5% edge:

TC 0 → house has slight edge, bet minimum.
TC +1 → roughly even.
TC +2 → player edge, bet 2× minimum.
TC +3 → bigger edge, bet 3–4× minimum.
TC +4+ → maximum bet.

This betting ramp is where all the profit lives. Playing decisions matter less than bet sizing — a counter making the same bet every hand barely beats a basic-strategy player.

Why counting is legal but casinos hate it

Counting cards is not cheating. You aren't marking cards, colluding with a dealer, or hiding a device. You're doing math in your head with public information. In most jurisdictions (including Nevada) casinos have no legal claim against you for using your brain.

What casinos can do — because they're private property — is refuse your action. If a pit boss suspects counting, they'll typically:

Watch your bet spread. Huge jumps from minimum to maximum after a run of low cards is the giveaway.
Instruct the dealer to shuffle earlier than usual, killing your penetration.
Ask you to flat-bet (same bet every hand).
Back you off — politely tell you to leave the blackjack table.
Trespass you from the property in extreme cases.

None of this happens online, where you can't count anyway because most sites use continuous shuffling.

What actually kills the edge in practice

Counting works on paper. In casinos it's brutal, and most people who "learn to count" never win money. The killers:

Penetration. If the dealer shuffles at 50% of the shoe, half your edge disappears. Modern casinos cut deep on purpose to shrink counter EV. You want 75%+ penetration to be worth playing.
Bet spread. You need to bet 8–16× your minimum at high counts to make real money. Do that on a $25 table and you're betting $400 on some hands. Do it obviously and you get backed off.
Variance. Even with a 1% edge, hourly swings of ±$500 are normal. Bankroll requirements are typically 1000+ units to weather the drawdowns.
Errors. A single misplay per shoe erases most of the edge. You have to count, convert to true count, adjust bet size, adjust strategy, chat with the pit, tip the cocktail server, and never look like you're doing math. It's harder than it sounds.

Deviations — where counting changes basic strategy

Once you know the true count, a handful of basic-strategy plays flip. These are the Illustrious 18 — the 18 highest-value deviations. A few examples:

16 vs 10 — basic strategy says hit. Deviation: stand at TC ≥ 0. The deck is only slightly ten-rich and standing already becomes correct.
12 vs 3 — basic strategy says hit. Deviation: stand at TC ≥ +2.
Insurance — basic strategy says never take it. Deviation: take insurance at TC ≥ +3. This is the single most profitable deviation and the one every counter learns first.
10 vs 10 — basic strategy says hit. Deviation: double at TC ≥ +4.

Drilling these is what our deviation trainer is for.

How to learn it without going to a casino

Counting is a skill stack. Trying to learn all of it at a real table is expensive and slow. Build it in layers:

Basic strategy first. Non-negotiable. If you can't play the base game blindfolded, you can't count.
Hi-Lo card counting drill. Flash cards at increasing speeds. Goal: perfect count on a full deck in under 25 seconds.
True count conversion drill. Practise dividing running count by decks remaining, on the fly.
Deviation drill. Layer the Illustrious 18 on top of basic strategy.
Live-fire practice. Deal to yourself, count, size bets, track EV over 1000 hands. Then, and only then, take it to a casino.

Realistically most people don't count for money — they learn it because it's a rare piece of math that actually beats a casino, and because knowing it makes them dramatically better at basic-strategy play too.

Frequently asked

Is card counting illegal? No, not in the US, UK, or most European jurisdictions. Casinos can still ban you as a private-property owner.

Can you count online? Almost never. Live-dealer games use continuous shuffling machines or shuffle after every shoe. RNG games shuffle after every hand.

How much do counters make? A skilled counter with a $10,000 bankroll on a $25 table earns roughly $25–50 per hour in EV, with huge variance. It's not a career for most people.

Do I need to be a math genius? No. Hi-Lo is addition and subtraction of +1, 0, −1. The hard part is speed and stamina, not math.

What's the fastest way to test if I can actually count? Take the Hi-Lo drill. Deal through a full deck, keep the running count, and check that you land on 0. If you're within ±1 in under 30 seconds, you have the aptitude.