Part III: Business & Regulation · Gambling Mathematics & Probability

24. Hi-Lo System (High-Low System)

Blackjack Math

The Hi-Lo System, also known as the High-Low or Plus-Minus system, is the most widely taught and commonly used card counting system in blackjack. It assigns point values to cards: 2-6 are counted as +1 (low cards), 7-9 as 0 (neutral), and 10-Ace as -1 (high cards). Because there are equal numbers of +1 and -1 cards in each deck, Hi-Lo is a balanced count — the running count returns to zero after a complete deck has been counted. The system’s popularity stems from its optimal balance of simplicity and effectiveness, with a betting correlation of 0.97 and a playing efficiency of 0.51. Surveillance personnel are trained to recognize the betting patterns and playing deviations characteristic of Hi-Lo counters.

In practice

The Hi-Lo system was developed by Harvey Dubner and popularized by Stanford Wong and others. It is a Level 1 system (only uses values of -1, 0, and +1), making it relatively easy to learn. Most card counting teams use Hi-Lo as their primary system.

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