Card Counting, Explained

Card counting is the only widely practical way to play blackjack with an edge over the house. The edge is smaller and harder to earn than the movies suggest, and every casino works to take it away. The Card Counting Course that teaches it is free.

Why counting works at all

Blackjack has memory. Every card dealt changes what is left in the shoe, and the remaining mix changes the odds. A shoe rich in tens and aces favors you: more blackjacks (paid 3:2), better doubles, and a dealer who busts more, because the dealer must hit stiff hands and big cards break them. A shoe rich in small cards favors the house for the same reasons reversed. Counting tells you which of those shoes you are in, so you bet more when the shoe favors you.

How Hi-Lo works

The standard Counting System, Hi-Lo, assigns every card a tag: 2–6 count +1, 7–9 count 0, tens and aces count −1.

You add the tags of every card you see. That sum is the running count. A high running count means many small cards have left the shoe, so what remains is rich in big cards.

A running count of +5 means more with one deck left than with five, so you divide by the decks left to get the true count, the number that sets your bet and your Index Plays. Each point of true count is worth about half a percent of edge. A high true count also changes a handful of plays, such as standing on 16 vs 10 at a positive count. Those are the Index Plays. The count also tells you when insurance, normally a losing bet, becomes profitable.

Is it legal?

Yes. Counting cards in your head is thinking, and thinking is not cheating anywhere. No one has ever been criminally charged for card counting itself. But casinos are private businesses. In most jurisdictions they can ask you to leave, restrict you to flat bets, or ban you. Atlantic City is the notable exception: New Jersey casinos cannot exclude counters, so they shuffle more instead. Using a device to count, such as a phone or an app, is a crime in Nevada and elsewhere. Count in your head only.

What casinos do about it

Casinos shuffle with a deck or two still undealt, which cuts off the count before it gets high. Some use continuous shuffle machines, which end counting entirely. Many pay 6:5 on blackjack, which cuts the counter's main payoff. Surveillance watches for the counter's signature, big bet jumps that track the count. Working counters spend as much effort hiding their bet spread as playing it.

The realistic numbers

A skilled solo counter at a good table earns roughly a 0.5–1.5% edge. That is not per hand won. It is on money wagered, over thousands of hands, through large swings. With a $10,000 bankroll and disciplined bet sizing, that is hourly earnings comparable to a decent job, and variance that will hand you losing weeks. It is a grind, and the casino is watching for you the whole time. You can put exact numbers on your own version of it with our free betting & risk calculator. For most players, perfect basic strategy at 3:2 tables is the better deal. It keeps most of the value and draws no heat.

If you want to learn anyway

It is a fun skill. Make basic strategy automatic first, in the trainer. Counting is useless while you are still thinking about the chart. Then take the free Card Counting Course. It covers Hi-Lo from card tags through true count, bet sizing, and Index Plays, with a graded Checkpoint in every Lesson. Between Lessons, keep sharp on the counting trainer's standalone Counting Exercises. The Course and the trainer are free.