Twenty-One

How Hi-Lo card counting actually works

Counting cards is not memorising which cards have gone. It is keeping one small number in your head that says whether what is left in the shoe favours you or the house — and then betting and playing differently when it does.

A shoe rich in tens and aces is good for the player: you get more blackjacks, which pay 3:2, and the dealer busts more often on the stiff hands they are forced to draw to. A shoe rich in small cards is good for the house. Hi-Lo measures which of those two you are sitting in, using a single running total.

Step one: the card tags

Every card gets one of three values. This is the whole system.

Hi-Lo card tags
CardsWhy
+12, 3, 4, 5, 6The small cards. Every one of them dealt out is one fewer card that can bust the dealer later.
07, 8, 9Neutral. They are counted as zero, which in practice means you skip them.
−110, J, Q, K, AThe cards you want left in the shoe: they make blackjacks and they bust stiff dealer hands.

Hi-Lo is balanced: there are as many +1 cards in a deck as −1 cards, so counting an entire deck down lands you back on exactly zero. That is not trivia — it is the self-check. If you count a full deck and do not finish on zero, you made a mistake, and you know it without anyone telling you.

Drill the tags and the countdown Tag speed first, then a full 52-card deck against the clock.

Step two: the running count

Start at zero when the shoe is shuffled. Add each card’s tag as it appears — every card, including the other players’ and the dealer’s. That total is the running count.

The skill worth building early is cancelling. A ten and a five on the table are +1 and −1, so they are nothing; see them as a pair and move on rather than adding them one at a time. Counters read a table in cancelled pairs, which is how they keep up with a fast dealer.

Step three: the true count

A running count of +8 means something completely different with one deck left than with five. Divide it out:

true count = running count ÷ decks remaining

Decks remaining is estimated by eye, from the discard tray. A rough estimate genuinely is enough — half a deck of error is tolerable, and nobody is counting cards to three decimal places. In a 6-deck shoe cut at 4.5 decks, you are dividing by something between 6 and about 1.5.

Every decision uses the true count, never the running count. That applies to how you bet and to every index play.

Step four: betting the count

The count is only worth money if your bet is bigger when the count is good. Each +1 of true count is worth roughly half a percent to the player, so the bet should climb with it. The ramp the trainer grades against spreads from one unit to 15:

Bet ramp by true count
Bet
below +2 to +11 unit
+2 to +22 units
+3 to +34 units
+4 to +48 units
+5 and above15 units

The published benchmark for this shape of game — 6 decks, cut 75% in, a 1–15 spread — is about a 1.15% player advantage. That is the whole prize: a hair over one percent, earned by playing perfectly for hours. Counting is not a fast way to make money, and a 1–15 spread is conspicuous. The individual rungs above are a convention rather than a sourced optimum, which is why the trainer shows you the ramp instead of hiding it.

Step five: playing the count

Betting captures most of the edge, but not all of it. When the count is high enough, a handful of hands should be played differently from the chart — standing on 16 against a ten, taking insurance, doubling tens. Those are the Illustrious 18 and the Fab 4, and knowing roughly that set captures 80 to 85% of everything available from deviating at all.

Put it together Keep the count yourself, size the bet off it and take the index plays — graded per shoe.

Counting cards in your head is legal. You are doing arithmetic about public information. No jurisdiction treats that as cheating, and using a device to do it for you is a different matter entirely and is generally a crime.

What casinos can do is refuse your business. They are private property; they can ask you to stop playing blackjack, bar you from the property, flat-bet you, or shuffle early. That is the real constraint on counting, and it is why the spread in the table above is a trade-off rather than a maximum.

Common questions

What is the difference between the running count and the true count?

The running count is the raw total of the card tags since the shuffle. The true count divides that by the number of decks still to be dealt, which is what makes the number comparable across the shoe. A running count of +8 with one deck left is a true count of +8; with four decks left it is +2. All betting and playing decisions use the true count.

Do I have to count every card at the table?

Yes — every card that is exposed, including other players hands and the dealer hole card once it is turned. The count measures what is left in the shoe, so every card that leaves it matters regardless of who it went to.

How much can card counting actually win?

For a 6-deck shoe cut at 4.5 decks with a 1 to 15 bet spread, the published benchmark is roughly a 1.15% advantage to the player. It is a small edge that only pays over a very large number of hands.

Is counting cards illegal?

No. Keeping a count mentally is legal — it is arithmetic on information everyone at the table can see. Using a device or an app to count for you at the table is a separate matter and is generally a criminal offence. Casinos are private property and may still bar you from playing.

Why is Hi-Lo the system people learn first?

It is level one, so every card is worth +1, 0 or minus 1 with no fractions, and it is balanced, so a full deck counts down to zero and you can check yourself. It has a betting correlation of .97, which captures nearly all of the available betting edge, and every published index play chart is written for it.