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Quick answer: Card counting is a way of tracking which cards have left a blackjack shoe, so you know when the remaining cards favour you. You add and subtract simple values as cards appear, convert that to a “true count”, and bet more when it’s high. Done well in a good game, it can turn the usual house edge of about 0.5% into a player edge of roughly 0.5–1.5%. It’s legal in the US as long as you only use your head, but casinos can refuse your action, and it doesn’t work in online RNG blackjack.
| Card counting at a glance | |
|---|---|
| Most popular system | Hi-Lo (2–6 = +1, 7–9 = 0, 10–A = −1) |
| Key number | True count = running count ÷ decks left to deal |
| Edge per +1 true count | About +0.5% for the player |
| Realistic player edge | About 0.5–1.5%, typically around 1% |
| Typical bet spread (shoe games) | About 1–8 to 1–15 |
| Legal? | Yes in the US without devices; casinos can still ban you |
| Works online? | Not in RNG games, which reshuffle every hand |
Why does card counting work?
In blackjack, a shoe that is rich in 10s and aces helps the player: you get more blackjacks (paid 3:2), your double downs land on 10s more often, and the dealer, who must hit stiff totals like 12–16, busts more. A shoe full of small cards helps the dealer. Counting doesn’t predict the next card. It tells you when the balance of what’s left has tipped in your favour, so you can bet more in those moments and less the rest of the time. Edward Thorp sized those bets with the Kelly criterion, which sets each stake as a share of your bankroll based on your edge.
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How does the Hi-Lo count work?
| Cards | Value |
|---|---|
| 2, 3, 4, 5, 6 | +1 |
| 7, 8, 9 | 0 |
| 10, J, Q, K, A | −1 |
Hi-Lo is a balanced count: there are as many +1 cards as −1 cards, so if you count through a full deck you end at zero. It was introduced by Harvey Dubner in 1963 and is still the system most players learn first.
Step 1: keep the running count
Start at 0 after a shuffle and add each card’s value as it’s dealt, yours, other players’ and the dealer’s. If the first hand shows 5, K, 3, 9 and A, the running count is +1 −1 +1 +0 −1 = 0.
Step 2: convert to the true count
A running count of +6 means much more with one deck left than with five. So you divide by the number of decks still to be dealt: true count = running count ÷ decks remaining. A running count of +6 with 3 decks left is a true count of +2.
Step 3: bet with the count
Each +1 of true count adds roughly 0.5% to your expected return. Starting from a house edge of about 0.5%, you break even around a true count of +1 in a good game and gain from there. Counters keep a minimum bet when the count is low and raise it as the true count climbs. The ratio between your smallest and largest bet is your bet spread; sources describe ramps from about 1–8 up to 1–15 in shoe games. Poor rules push the break-even point higher. A 6:5 payout adds about 1.4% to the house edge (see our basic strategy chart), and at roughly 0.5% per true count you would need a true count about three points higher before you have an edge. That is why counters avoid those tables.
What is each true count worth in money?
First, why a full deck counts to zero. The 2s to 6s are five ranks × 4 suits = 20 cards at +1. The 10s, jacks, queens, kings and aces are another 20 cards at −1. The 7s, 8s and 9s are 12 cards at 0. So 20 − 20 = 0, and any count away from zero tells you which cards are left.
Next, the money. We worked this out with the rule of thumb above: start from a house edge of about 0.5% and move about 0.5% to your side for each +1 of true count. Your average result per hand is your bet × your edge. Here it is with a £10 minimum bet and a 1–8 spread:
| True count | Your edge (approx.) | Bet | Average result per hand |
|---|---|---|---|
| 0 or lower | −0.5% or worse | £10 | £10 × −0.5% = −£0.05 or worse |
| +1 | About 0% | £10 | About £0 |
| +2 | +0.5% | £20 | £20 × 0.5% = +£0.10 |
| +3 | +1.0% | £40 | £40 × 1.0% = +£0.40 |
| +4 | +1.5% | £60 | £60 × 1.5% = +£0.90 |
| +5 or higher | +2.0% or more | £80 | £80 × 2.0% = +£1.60 or more |
Two things stand out. Most hands in a shoe are dealt at counts near zero, where you bet small and lose a little. Nearly all the profit comes from the fewer hands at high counts, when your bet is biggest. That is why counters need a bet spread, and why their results swing so much from session to session.
What a counter can realistically expect
Published estimates put the long-run edge of a skilled counter at around 0.5–1.5%, typically about 1%, under good conditions. That’s an advantage measured over thousands of hands, with big swings along the way. It also assumes accurate counting, basic strategy played perfectly and casinos that let you keep playing.
Conditions that make or break counting
- Penetration: the share of the shoe dealt before the shuffle. Counting needs deep penetration, roughly 75% or more; if the dealer cuts off half the shoe, the high counts rarely arrive.
- Continuous shuffling machines: cards go back into the machine after each hand, so the count never builds. Counting is pointless against them.
- Online RNG blackjack: the virtual deck is reshuffled every hand. Counting can’t work.
- Live dealer blackjack online: real shoes, but they are often shuffled early, which removes most of the value.
- Table rules: 3:2 blackjack and favourable rules lower the count you need. See our blackjack rules guide for the rules that matter.
Is card counting legal?
In the US, counting cards in your head isn’t a crime and isn’t cheating. Using help is a different matter: in Nevada, NRS 465.075 makes it unlawful to use or carry a device or software designed to track cards.
Being legal doesn’t mean casinos must let you play. In Nevada, casinos can refuse a player’s action or ask them to leave for counting. New Jersey is the main exception: in Uston v. Resorts International (1982), the state’s Supreme Court held that Atlantic City casinos couldn’t bar counters, though they can still use countermeasures such as more decks and shallower penetration. Rules differ elsewhere, so check the laws where you play.
Wonging and other counting systems
Wonging (back-counting) means counting a table from behind without playing, then joining only when the count turns positive. It’s named after the author Stanford Wong.
| System | Type | Level | Notes |
|---|---|---|---|
| Hi-Lo | Balanced | 1 | The standard starting system |
| KO (Knock-Out) | Unbalanced | 1 | Counts 7s as +1, so no true-count conversion is needed |
| Hi-Opt I | Balanced | 1 | |
| Omega II | Balanced | 2 | Multi-level values; more accurate but harder to keep |
A short history
Edward O. Thorp’s Beat the Dealer, published in 1962, is widely regarded as the original guide to card counting. Later, the professional counter Ken Uston took Resorts International to court over being barred in Atlantic City and won in 1982.
Should you try it?
Card counting is a real, mathematically sound technique, but it’s demanding: hours of practice, a large bankroll to ride out swings, and the risk of being asked to leave. For most players, learning basic strategy (which brings the house edge down to about 0.5%) and choosing tables with good rules is the bigger win. Our low house edge games list shows where blackjack sits against other games.
If you play online, our top-rated casino 1win (9.9/10) has blackjack tables; use the promo code Ultragambler if you sign up. Remember that counting doesn’t work in online RNG games. Online gambling isn’t legal everywhere, so check your local laws, and only stake what you can afford to lose.
How we checked this
- Hi-Lo card values, the true count, penetration and shuffling machines: Wikipedia and Wizard of Odds. KO as an unbalanced count with no true-count step: Wikipedia and Blackjack Apprenticeship.
- Harvey Dubner introducing Hi-Lo in 1963: Wizard of Odds and Stacker. Thorp’s Beat the Dealer in 1962: Wikipedia and Stacker.
- About 0.5% per true count and break-even near +1: Blackjack Apprenticeship and DeucesCracked, whose +2 example works out at the same rate.
- A realistic edge of about 0.5–1.5%, and bet spreads up to about 1–15: Wizard of Odds and DeucesCracked.
- The law: NRS 465.075 on the Nevada Legislature site, and Uston v. Resorts International (New Jersey Supreme Court, 1982) in Wikipedia and Quimbee’s case summary.
- Our maths: the full-deck balance check, the money table and the higher break-even count for 6:5 games are our own calculations from the figures above.
Last checked: 13 October 2026, when we worked out what each true count is worth per hand ourselves and confirmed the remaining figures with two or more independent sources.
Card counting FAQ
Is card counting illegal?
Not in the US, as long as you count in your head. Using a device to track cards is illegal in Nevada. Casinos can still refuse to let you play, except that New Jersey casinos can’t bar counters.
How much can you win counting cards?
A skilled counter in a good game might expect an edge of around 0.5–1.5% of the money bet. Short-term results swing a lot, and you need a big bankroll to ride them out.
Can you count cards online?
Not in RNG games, because the deck is reshuffled every hand. Live dealer games use real shoes, but they are often shuffled too early for counting to help much.
What is a good true count?
In a good shoe game you roughly break even at a true count of +1, and each extra point adds about 0.5% to your edge. Counters raise their bets as the true count climbs above that.
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