Card counting in blackjack: what it is, what it isn't, and how to actually do it.
Counting is one trick: track which cards are gone, bet more when what's left favours you. It's legal, learnable in an afternoon, and the edge is real but small. Here's the whole picture.
Tens favour the player. Counting tells you when they’re coming.
A shoe rich in tens and aces is good for you and bad for the dealer. You make more blackjacks (paid 3:2). You make stronger doubles. And the dealer, forced to draw to a stiff 12–16, busts far more often.
Counting is one trick: keep a running tally of how the shoe's mix has shifted as cards come out. When the tally tips positive, the remaining shoe is high-card heavy and the house edge briefly flips your way. You bet more in those moments and less in the others.
The standard system. Three tags. Done.
Hi-Lo is the most-taught system in the world because the tags are symmetric and trivially memorable.
As each card is dealt (yours, the dealer's, every other player's), add its tag to your running count. The full deck sums to zero (it's a balanced system), so a true shuffle resets you to neutral.
Divide by decks remaining.
A running count of +6 means very different things in a 6-deck shoe with 5 decks left (mildly positive) vs. with 1 deck left (extremely positive). To compare apples to apples, convert to true count:
That's the number you actually act on. Bet decisions and count-based deviations use true count, not running.
Decks remaining is eyeballed from the discard tray, not measured. Within ¼ of a deck is fine. With practice it's instant.
KO is simpler. Omega II is sharper. Pick one.
KO (unbalanced)
Identical to Hi-Lo except 7 is also +1. Because the full deck sums to +4 instead of 0, you skip the true-count division entirely: bet decisions key off the running count directly. Lower mental overhead, slightly less precise.
Omega II (multi-level)
Multi-level tags for higher accuracy: 4, 5, 6 each = +2; 2, 3, 7 each = +1; 8 = 0; 9 = −1; tens = −2; Ace = 0 (tracked separately as a side count). About 10–15% more accurate than Hi-Lo, with materially more cognitive load.
Master Hi-Lo first. Switch systems only if you've actually squeezed everything out of it, which most people never do.
Where the edge actually comes from.
Counting accurately is worthless if you bet the same amount every hand. Your edge comes from betting more in positive counts and less in negative ones. The wider the spread, the bigger your edge, and the more obvious you look to a pit boss.
A common spread for a 6-deck shoe: 1 unit at TC ≤ +1, then 2, 4, 6, 8, 10 units as the true count climbs. Most professionals cap their spread at the table's tolerated ratio (usually 1:8) to stay under the radar.
The Illustrious 18, when basic strategy isn’t enough.
At extreme true counts, the chart-correct play changes. The most famous example: insurance, which is a losing bet at neutral count, becomes positive EV at true count ≥ +3.
The Illustrious 18is Don Schlesinger's shortlist of the 18 deviations that capture the bulk of the EV from count-based play. Examples:
- Insurance at TC ≥ +3
- 16 vs. 10: stand at TC ≥ 0
- 15 vs. 10: stand at TC ≥ +4
- 12 vs. 3: stand at TC ≥ +2
- 10 vs. A: double at TC ≥ +4
Don't learn deviations until basic strategy and the count are both automatic. Adding them too early hurts your accuracy on every cell.
It’s legal. It’s also brutal.
- Edge is small. Even a perfect counter at a decent table earns ~0.5–1.5% over the house. Hourly EV is a function of bet size, hands per hour, and discipline.
- Variance is huge.You'll have losing sessions, losing weeks, sometimes losing months. The edge only shows over thousands of hands.
- Casinos hate it but it's not illegal. They will back you off the game, or 86 you from the property. Casinos can refuse service for any reason.
- Continuous shufflers kill it. CSMs (continuous shuffle machines) reshuffle every round. No deck depth, no count. Avoid those tables.
Reading doesn't train the muscle. Counting does.
Turn on count training in the trainer and it quizzes you between rounds (running count, true count, or both). Cheap reps, fast feedback.