What Is Card Counting?

Card counting is a blackjack technique where you track the ratio of high cards to low cards remaining in the deck. When the remaining cards are disproportionately rich in 10s and Aces, the player has an advantage over the house.

It’s not about memorizing every card. It’s about maintaining a simple running total that tells you whether conditions are favorable.

Why It Works

Blackjack is unique among casino games because past events affect future probabilities. Once cards are dealt, they’re removed from the shoe. This means:

  • A deck rich in 10s and Aces benefits the player:
    • More natural blackjacks (which pay 3:2)
    • Better double down outcomes
    • Dealer busts more often on stiff hands (12-16)
  • A deck rich in low cards (2-6) benefits the dealer:
    • Dealer draws to better hands instead of busting
    • Fewer natural blackjacks for the player

The Hi-Lo System

The Hi-Lo (High-Low) system is the most popular card counting method. It was developed by Harvey Dubner and refined by Stanford Wong.

Card Values

Card Count Value
2, 3, 4, 5, 6 +1
7, 8, 9 0
10, J, Q, K, A -1

How to Use It

  1. Start at 0 when a fresh shoe begins
  2. Add or subtract as each card is revealed
  3. Keep a running count throughout the shoe
  4. Convert to a true count by dividing by remaining decks

Example

Cards dealt: 5, K, 3, 8, A, 2, 10, 6, 7, Q

Card Value Running Count
5 +1 +1
K -1 0
3 +1 +1
8 0 +1
A -1 0
2 +1 +1
10 -1 0
6 +1 +1
7 0 +1
Q -1 0

True Count

The running count tells you the raw balance of high vs. low cards. But its significance depends on how many decks remain.

True Count = Running Count ÷ Decks Remaining

A running count of +6 with 2 decks remaining (true count = +3) is much more significant than +6 with 6 decks remaining (true count = +1).

Why It Matters

True count determines:

  • Bet sizing — higher true count = bigger bets
  • Strategy deviations — some plays change based on the count
  • The actual player edge — roughly 0.5% per true count above +1

Bet Sizing

The key to profiting from card counting is varying your bets:

  • Low/negative count: Bet the minimum (the house has the edge)
  • True count +1: Standard bet
  • True count +2: 2x standard bet
  • True count +3: 4x standard bet
  • True count +4+: 6-8x standard bet

This is called a bet spread. A typical counter uses a 1:8 or 1:12 spread.

Other Counting Systems

System Level Accuracy Difficulty
Hi-Lo 1 Good Easy
KO (Knockout) 1 Good Easiest (no true count conversion)
Hi-Opt I 1 Better Moderate
Hi-Opt II 2 Excellent Difficult
Omega II 2 Excellent Difficult
Wong Halves 3 Highest Very Difficult

Level refers to the range of values assigned to cards. Level 1 systems use only +1, 0, -1. Higher levels use additional values for greater accuracy but are harder to use.

Casino Countermeasures

Casinos actively combat card counting:

  • Multiple decks — 6 and 8-deck shoes reduce counting effectiveness
  • Frequent shuffling — less deck penetration limits the count’s usefulness
  • Continuous shuffling machines (CSMs) — reshuffle after every hand
  • Surveillance — casinos watch for bet-spreading patterns
  • Back-offs — politely asking you to stop playing blackjack
  • Banning — being prohibited from the casino
  • Reduced deck penetration — shuffling earlier in the shoe

Realistic Expectations

Card counting in practice is very different from movies:

  • Small edge: Even expert counters only gain 0.5-1.5% over the house
  • Huge variance: Thousands of hands are needed to see the edge manifest
  • Large bankroll required: You need 200-300 betting units minimum
  • Hours of grinding: Most of your time is spent flat-betting at minimum
  • Casino heat: You must avoid detection, which limits bet spreads
  • It’s work: Maintaining concentration for hours is mentally exhausting

Card counting is a legitimate mathematical technique, but it’s far from the easy money Hollywood portrays.