Hi-Lo vs Omega II vs Hi-Opt II: Comparing Card Counting Systems

Hi-Lo is the most popular card counting system. It's also not the most accurate.

So why do most professionals use it? And when do advanced systems actually make sense?

This post breaks down the major counting systems, their tradeoffs, and helps you decide which one fits your goals.

The Spectrum of Counting Systems

Card counting systems exist on a spectrum from simple to complex:

Simple ←————————————————————————————→ Complex
  KO     Hi-Lo     Hi-Opt I     Hi-Opt II     Omega II     Wong Halves

Generally, more complex systems are more accurate. But accuracy isn't everything—you also need to be able to execute the system flawlessly under casino conditions.

Hi-Lo: The Industry Standard

Card Values: | Cards | Count | |-------|-------| | 2-6 | +1 | | 7-9 | 0 | | 10-A | -1 |

Strengths: - Simple addition and subtraction - Balanced (ends at zero with full deck) - Well-documented strategy deviations - Fast to learn and execute

Weaknesses: - Treats all low cards equally (a 5 is more valuable to the house than a 2) - Treats all high cards equally (an Ace is more valuable for player than a 10) - Not optimized for betting correlation OR playing efficiency—it's a compromise

Betting Correlation: 0.97 Playing Efficiency: 0.51

The betting correlation (BC) measures how well the count predicts when to bet big. The playing efficiency (PE) measures how well it predicts strategy deviations. Hi-Lo's BC is excellent; its PE is mediocre.

This is fine. Betting correlation matters more for profit. About 80% of your edge comes from bet variation, only 20% from strategy deviations.

KO (Knock-Out): Simplicity First

Card Values: | Cards | Count | |-------|-------| | 2-7 | +1 | | 8-9 | 0 | | 10-A | -1 |

The key difference: 7s are +1 instead of 0.

Strengths: - No true count conversion needed (it's "unbalanced") - Even simpler than Hi-Lo in practice - Good for beginners

Weaknesses: - Less accurate than Hi-Lo - Unbalanced nature means the "pivot point" (where you have an edge) depends on decks

Betting Correlation: 0.98 Playing Efficiency: 0.55

KO's secret weapon is that you don't divide by decks remaining. The running count is your betting signal. This eliminates an error-prone step and lets you focus purely on tracking cards.

For casual counters or those who struggle with true count division, KO is often the better choice despite lower theoretical accuracy.

Hi-Opt I: Improved Playing Efficiency

Card Values: | Cards | Count | |-------|-------| | 2, A | 0 | | 3-6 | +1 | | 7-9 | 0 | | 10-K | -1 |

Note: 2s and Aces are zero. This seems counterintuitive—aren't Aces good for the player?

Yes, but they're weird. An Ace is good for blackjacks (player advantage) but also helps dealer make hands from stiff positions (house advantage). Its net effect is closer to neutral than Hi-Lo assumes.

Strengths: - Better playing efficiency than Hi-Lo - 2s are neutral (correctly reflects their minor impact) - Still relatively simple

Weaknesses: - Requires a separate Ace side count for insurance decisions - Less documentation than Hi-Lo

Betting Correlation: 0.88 Playing Efficiency: 0.61

Hi-Opt I trades betting correlation for playing efficiency. If you're going to use many strategy deviations, this matters. If you're primarily varying bets, Hi-Lo is better.

Hi-Opt II: The Balanced Upgrade

Card Values: | Cards | Count | |-------|-------| | 2, 3, 6, 7 | +1 | | 4, 5 | +2 | | 8, 9 | 0 | | 10-K | -2 | | A | 0 |

Now we're using multiple count values. 4s and 5s are +2 because they're the most damaging cards for the player. 10s through Kings are -2 because they're the most valuable.

Strengths: - Excellent accuracy - Better reflects the true value of cards - High playing efficiency

Weaknesses: - Multiple count values slow you down - Still requires Ace side count - Requires true count conversion

Betting Correlation: 0.91 Playing Efficiency: 0.67

Hi-Opt II is popular among serious amateurs. The +2/-2 values for the most impactful cards improve accuracy meaningfully. The question is whether you can maintain that accuracy at casino speed.

Omega II: The Academic's Choice

Card Values: | Cards | Count | |-------|-------| | 2, 3, 7 | +1 | | 4, 5, 6 | +2 | | 8, A | 0 | | 9 | -1 | | 10-K | -2 |

Omega II adds another wrinkle: 9s are -1. This reflects that 9s are slightly beneficial to the player (good for making 19, 20).

Strengths: - One of the most accurate level-2 counts - Excellent for single-deck games - Published in "Blackbelt in Blackjack" with extensive documentation

Weaknesses: - Five different count values (+2, +1, 0, -1, -2) - Requires Ace side count - Easy to make errors under pressure

Betting Correlation: 0.92 Playing Efficiency: 0.67

Omega II is often cited as the best balanced level-2 count. Whether it's worth the complexity depends on your execution ability.

Wong Halves: Maximum Accuracy

Card Values: | Cards | Count | |-------|-------| | 2, 7 | +0.5 | | 3, 4, 6 | +1 | | 5 | +1.5 | | 8 | 0 | | 9 | -0.5 | | 10-A | -1 |

Yes, those are fractions. Most users double everything to work with integers: 5 becomes +3, 9 becomes -1, etc.

Strengths: - Extremely accurate - Well-suited to single and double deck

Weaknesses: - Fractional values are brutal in practice - Seven different count values - Very high error rate under real conditions

Betting Correlation: 0.99 Playing Efficiency: 0.57

Wong Halves demonstrates the theoretical limit of counting system accuracy. In practice, almost no one uses it. The error rate exceeds the theoretical gain.

The Accuracy vs. Execution Tradeoff

Here's the core insight most counting guides miss:

A simpler system executed perfectly beats a complex system executed with errors.

Let's model this. Assume: - Hi-Lo at 95% accuracy = 95% × 0.97 BC = 0.92 effective BC - Omega II at 85% accuracy = 85% × 0.92 BC = 0.78 effective BC

Your error rate matters more than the system's theoretical accuracy.

This is why professionals often stick with Hi-Lo. They've drilled it until it's automatic. They can track count, estimate decks, calculate true count, adjust their bet, engage in camouflage conversation, and watch for pit boss attention—all simultaneously.

Adding mental load to the count itself breaks something else.

Side Counts: The Real Complexity

Many advanced systems require "side counts"—tracking specific cards separately:

Ace side count: Track how many Aces have been played vs. expected. Used for insurance decisions and blackjack probability.

5 side count: Some players track 5s separately because they're the most impactful single card.

Side counts multiply complexity dramatically. You're now maintaining two running counts simultaneously, then combining them for decisions.

For most players, the value isn't there. For professionals playing hours daily, they might add 0.1-0.2% edge.

My Recommendation

For beginners: Start with Hi-Lo. It's the standard for a reason. Extensive documentation, well-known index plays, and proven effectiveness.

For casual players: Consider KO. The elimination of true count conversion makes it more robust against mistakes.

For serious hobbyists: Hi-Lo with the "Illustrious 18" index plays and "Fab 4" surrender indices. This covers 90%+ of the value from strategy deviations.

For aspiring professionals: Master Hi-Lo first. If you can maintain 99%+ accuracy under casino conditions, then consider Hi-Opt II or Omega II. Most people never reach this threshold.

For academic interest: Study Wong Halves and understand why it's not used. The gap between theory and practice is the real lesson.

What Our Calculator Uses

The Advantage Player calculator uses Hi-Lo as the default because:

1. It's what most users know
2. It has the best documentation for index plays
3. Its high betting correlation matters most for real-world profit

But here's the thing: the calculator shows exact composition-dependent strategy. It doesn't rely on the simplified assumptions of any counting system. It knows exactly which cards remain and computes true probabilities.

This means you can see when the simplified count diverges from reality—and understand why.

Experiment with how count changes affect strategy in real-time. Try the calculator and watch the math update as you deal cards.