Card Counting 101: How It Works, What It Isn’t, and How to Practice

Card counting is a strategy for games like blackjack that tracks the ratio of high cards (10–A) to low cards (2–6) remaining in the shoe. When more high cards remain, player outcomes (like blackjacks and profitable doubles) tend to improve; when more low cards remain, the house edge climbs. This overview explains the core concepts, shows a simple worked example, and provides practice drills you can try at home.

Educational use only. House rules and laws vary by location. Using devices is often illegal; purely mental strategies may still get you backed off. Know and follow your local rules.

What Card Counting Actually Measures

• Composition, not prediction: You’re not “foretelling” the next card—you’re estimating whether the shoe is rich in highs or lows.
• Edge swings: In standard rules, basic strategy yields a small house edge. In favorable counts (more highs left), your expected value can swing positive.
• Betting and play deviations: Counters typically bet more when the count is favorable, and make small rule‑based deviations from basic strategy.

A Simple System: High‑Low (Hi‑Lo)

Assign values as cards are revealed:

• 2–6 = +1
• 7–9 = 0
• 10–A = −1

The running count is the sum of all tags seen. To adjust for remaining cards, convert to a true count:

True Count = Running Count ÷ Estimated Decks Remaining

Quick Example

In a 6‑deck shoe, after one deck has been dealt your running count is +8. You estimate ~5 decks remain. True count ≈ +8 ÷ 5 = +1.6 (round to +2). With a +2 true count, many counters raise bets slightly and may apply a few play deviations.

From Count to Decisions

• Bet sizing (bankroll‑aware): Scale bet size with true count (e.g., 1 unit at TC ≤ 0, 2–4 units at TC +1 to +2, more above that), staying within a risk plan.
• Play deviations: A small chart of changes from basic strategy based on TC (e.g., standing on 16 vs 10 at TC ≥ 0). Learn a short, high‑impact list first.
• Table selection: Fewer decks, deeper penetration (more of the shoe dealt), and player‑friendly rules improve counter effectiveness.

Practice Drills (At Home)

• Speed count: Flip through a deck, tagging +1/0/−1 out loud. Goal: return to 0 at the end; time yourself and reduce mistakes.
• True‑count conversion: Periodically stop and estimate decks remaining by eye; divide running count on the fly.
• Deviations flashcards: Keep 10–15 key plays and the counts they change on a pocket card; drill until automatic.

Common Pitfalls

• Inconsistent deck estimates: True count accuracy depends on your decks‑remaining estimate—practice the visual estimation.
• Heat and camo: Big, sudden bet jumps draw attention. Many players use smoother ramps and vary their play to blend in (at the cost of some EV).
• Overconfidence: Counting doesn’t guarantee wins in a session; it shifts long‑run expectation. Bankroll and variance management matter.

Ethics and Legality

• Devices vs. mental methods: Electronic or mechanical aids are widely illegal. Purely mental counting is often lawful but can still violate house policies.
• Casino rights: Private venues can refuse service or ask you to stop playing. Stay respectful and comply with staff requests.
• Know your jurisdiction: Laws vary. When in doubt, seek local legal guidance.

FAQs

Is card counting illegal? Laws vary. Using devices is often illegal; mental counting may be permitted but casinos can still bar players. This is not legal advice.

Can I beat blackjack with basic strategy alone? Basic strategy minimizes the house edge but does not overcome it by itself. Counting plus good rules and discipline are usually required to gain an edge.

How do I practice safely? Practice at home using a deck. For probability intuition and simulations, experiment with our card dealing tool at /other/deal-random-playing-cards.