How to Count Cards in Blackjack: The Hi-Lo System

Why counting works

Blackjack is the one casino game where the past changes the future. Once cards are dealt they are out of the shoe until the shuffle, so the mix of what is left keeps shifting. A shoe rich in tens and aces favors the player: more blackjacks (paid 3 to 2), more successful doubles, and a dealer who busts more often on stiff hands. A shoe rich in small cards favors the dealer.

Card counting is simply keeping track of that shift. You do not memorize cards. You keep one running number that tells you whether the remaining shoe is rich or poor in high cards, and you bet more when it is rich.

The Hi-Lo tags

Hi-Lo assigns every card a tag of +1, 0 or −1. It is a balanced count: a full deck adds up to zero.

Cards	Tag	Why
2, 3, 4, 5, 6	+1	Small cards leaving the shoe make it richer in high cards. Good for you.
7, 8, 9	0	Neutral. They barely move the odds.
10, J, Q, K, A	−1	High cards leaving the shoe make it poorer. Bad for you.

Memorize the tags until you see a 5 and think “plus one” without effort. That is the whole system. Everything else is arithmetic and discipline.

Keeping the running count

Start at 0 after the shuffle. Add the tag of every card you see, yours, other players’, and the dealer’s, including the dealer’s hole card when it is turned over. The number you are holding is the running count.

Two habits make it fast:

• Cancel pairs. A 10 and a 4 together are zero. Look for high-low pairs on the table and skip them.
• Count in pairs of cards, not one at a time. Two small cards are +2 in one glance.

Drill: deal a full deck face up, counting as fast as you can. You should land on exactly 0 (or the tag of a card you removed before you started, to make sure you are not cheating). Under 30 seconds with no errors is a solid goal. The Speed Counting mode in Blackjack AI Pro times this and checks your count at random points.

Converting to true count

A running count of +6 means very different things with five decks left and with one deck left. The true count fixes that:

True count = running count ÷ decks remaining

Estimate the decks remaining from the discard tray. In a 6-deck shoe with about two decks in the discards, four decks remain, so a running count of +8 is a true count of +2. Round down when in doubt; a conservative true count costs less than an optimistic one.

Each true count point is worth roughly half a percent of advantage. The house edge in a typical 6-deck H17 game is about 0.55 percent off the top, so the player pulls ahead around true count +1 and has close to a 1 percent edge at +3.

Betting with the count

The edge comes from betting more when the true count is high and the minimum, or nothing, when it is low. A bet spread is your plan for that. A common 6-deck ramp:

True count	Bet
+1 or lower	1 unit
+2	2 to 3 units
+3	4 to 5 units
+4	6 to 8 units
+5 and up	8 units (your maximum)

Wonging out, leaving the table or sitting out when the true count drops below −1, improves the win rate because you skip the rounds where the house has its biggest edge. Your bankroll decides how big a unit you can afford: run your spread through the bankroll calculator to see the risk of ruin, and read how far you are from the long run (N0).

Playing deviations

Basic strategy is the correct play for a neutral shoe. When the count moves, a handful of plays change. The most valuable ones are on the deviations chart, with four surrender plays added when late surrender is offered. The first few carry most of the value: take insurance at true count +3 or higher, stand on 16 vs 10 at 0 or higher, stand on 15 vs 10 at +4, and stand on 12 vs 3 at +2.

The full table with indexes for H17 and S17 is on the deviations chart page. The app’s Deviations mode drills them with trap hands, so you learn the index, not just the hand.

A practice routine that works

1. Basic strategy to 100 percent. Counting is pointless if your playing decisions leak. Use the chart and play hands until hard, soft and pair accuracy all sit at 100 percent for a week.
2. Deck countdowns, daily. Five minutes a day. Aim for under 30 seconds, zero errors.
3. Count while you play. Play practice hands with the count running and take count checks every few rounds. This is where most people find out their count falls apart under load.
4. Add the true count and the spread. Estimate decks remaining from the discard tray, convert, and bet the ramp.
5. Add deviations last. Drill the index plays only once the count is automatic.

Blackjack AI Pro was built around exactly this ladder: four modes, each graded, with stats that show which rung you are on.

Practice the count on a real 6-deck shoe in our free blackjack game, where the discard tray shows how many decks are gone.

Card counting FAQ

Is card counting illegal?

No. Counting cards in your head is legal in the United States and most of the world. Casinos are private businesses and may ask a player they suspect of counting to stop playing blackjack or to leave. Using a device to count is illegal in many jurisdictions, which is why you practice on your phone and play with your head.

How long does it take to learn to count cards?

Most people can keep a running count through a deck in a week of daily practice. Converting to true count and playing without errors at casino speed usually takes a few months. Speed drills shorten that, because the goal is a count that runs in the background while you play basic strategy perfectly.

What is the difference between running count and true count?

The running count is the sum of the Hi-Lo tags of every card you have seen since the shuffle. The true count divides it by the number of decks still to be dealt. Betting and playing decisions use the true count, because +6 with five decks left is much weaker than +6 with one deck left.

Does card counting work in 6-deck and 8-deck games?

Yes, as long as penetration is deep enough. A 6-deck shoe with 75 to 85 percent dealt is the standard counting game today. Shallow penetration and continuous shuffling machines kill the edge.

How much of an edge does a card counter have?

A typical Hi-Lo player with a 1 to 8 spread in a decent 6-deck game plays at roughly a 0.5 to 1 percent advantage over the long run, with big swings along the way. The bankroll calculator shows the win rate and variance for your exact spread and rules.