Blackjack Card Counting — The Hi-Lo System Explained

Card counting is not memorizing every card — it is tracking one number that tells you when the remaining shoe favors you. Hi-Lo is the most widely used system because it is simple and accurate, and it is the foundation every other count builds on.

The Hi-Lo card values

Each card you see gets a value, and you keep a running total:

• 2, 3, 4, 5, 6 → +1 (low cards leaving the shoe is good for you)
• 7, 8, 9 → 0 (neutral)
• 10, J, Q, K, A → −1 (high cards leaving is bad for you)

This is a balanced count: a full shoe sums to exactly zero, because there are as many +1 cards as −1 cards. You start at 0 after a shuffle and add each card's value as it is dealt — that total is the running count.

Why a high count favors the player

When lots of low cards have already been played, the shoe is rich in tens and aces, and that shifts several things your way at once:

• More blackjacks (which pay 3:2) for you — and the dealer.
• Your doubles win more often, because you draw a ten more often.
• The dealer busts more, because they must hit stiff totals into a ten-heavy shoe.
• Insurance and the surrender line on 16 vs 10 become correct that wouldn't be off the top of the deck.

The net of those effects is positive for the player, which is why counters bet more when the count is high and minimum when it is low.

From running count to advantage

A running count of +6 means very different things with six decks left versus one deck left. To turn the running count into an actual edge you divide by the decks remaining — the true count — covered in running count vs true count. As a rule of thumb, each +1 of true count is worth roughly half a percent of edge in Hi-Lo.

Hi-Lo is an estimate — Fullcount is the exact number

Hi-Lo deliberately throws away detail (every low card is +1, every ten is −1) so you can do it in your head at the table. That simplicity costs a little accuracy. Fullcount skips the approximation entirely: it computes the exact expected value of every action from the precise cards left in the shoe — the ground truth that Hi-Lo is trying to estimate. Enter the cards already out and compare:

Use Hi-Lo to know when the shoe is good while you play; use Fullcount to see exactly how good, and to check whether a borderline deviation is really correct. Start from the basic strategy overview, then see how the count changes specific plays in the basic-strategy matrix.