Blackjack card counting
Basic strategy assumes a freshly shuffled shoe. Card counting tracks the shoe as it depletes, and that is the one edge blackjack gives a skilled player.
Short answer
Card counting tracks the ratio of high cards to low cards left in the shoe. Hi-Lo, the standard system, tags every card +1, 0, or −1 as it is seen. Add the tags to get a running count, divide by the decks remaining to get a true count, then bet more and adjust a handful of plays as the true count rises. A full deck or shoe always nets to zero.
Step 1: The tags
| Cards | Tag |
|---|---|
| 2, 3, 4, 5, 6 | +1 |
| 7, 8, 9 | 0 |
| 10, J, Q, K, A | −1 |
Step 2: Running count
Start at zero. Add the tag of every card you see. A full deck or shoe always nets to zero, which is how you check yourself. Practice this until you can run through a deck quickly and land on the right number in the card counting trainer.
Step 3: True count
Divide the running count by the number of decks remaining. A running count of plus six with two decks left is a true count of three. The true count is what you actually bet and deviate on, because it measures how rich the shoe is, not just the raw total.
Step 4: Bet and deviate
The higher the true count, the more you bet. At certain true counts you also change a few basic-strategy plays. The most valuable changes are the Illustrious 18 and the Fab 4 surrenders below. Take insurance only when the true count is plus three or higher.
| Play | Deviation | True count index |
|---|---|---|
| Insurance | Take insurance | +3 |
| Hard 16 vs 10 | Stand | 0 |
| Hard 15 vs 10 | Stand | +4 |
| Pair of 10s vs 5 | Split | +5 |
| Pair of 10s vs 6 | Split | +4 |
| Hard 10 vs 10 | Double | +4 |
| Hard 12 vs 3 | Stand | +2 |
| Hard 12 vs 2 | Stand | +3 |
| Hard 11 vs A | Double | +1 |
| Hard 9 vs 2 | Double | +1 |
| Hard 10 vs A | Double | +4 |
| Hard 9 vs 7 | Double | +3 |
| Hard 16 vs 9 | Stand | +5 |
| Hard 13 vs 2 | Stand | −1 |
| Hard 12 vs 4 | Stand | 0 |
| Hard 12 vs 5 | Stand | −2 |
| Hard 12 vs 6 | Stand | −1 |
| Hard 13 vs 3 | Stand | −2 |
| Play | Deviation | True count index |
|---|---|---|
| Hard 14 vs 10 | Surrender | +3 |
| Hard 15 vs 10 | Surrender | 0 |
| Hard 15 vs 9 | Surrender | +2 |
| Hard 15 vs A | Surrender | +1 |
An index of 0 means the deviation is correct at a true count of zero or higher — in other words, it is actually the basic-strategy play already. A negative index means the deviation applies even at some negative true counts.
Practice it
The card counting trainer drills all four steps separately: running count at a speed you set, true count conversion, and the Illustrious 18 / Fab 4 deviations with the exact index for each, quizzed until they are automatic.
Common questions
Is card counting illegal?
No. It uses only information available to any player — the cards already dealt. Casinos dislike it and can refuse service to a suspected counter, but it is not against the law.
Do I need to memorize all 18 plus 4 deviations?
No. The Illustrious 18 and Fab 4 are already the highest-value subset, ranked by how much they're worth learning first; the first few (insurance, hard 16 vs 10, hard 15 vs 10) matter far more than the last few.
What is the difference between running count and true count?
The running count is the raw sum of Hi-Lo tags. The true count divides that by the decks remaining, which is what you actually bet and deviate on — a running count of +6 means very different things with one deck left versus six.