How Blackjack Card Counting Works
Card counting in Blackjack tracks the ratio of high cards (10s and Aces, which favor the player with 3:2 blackjacks and profitable double downs) to low cards (2 through 6, which help the dealer make stiff hands). When the remaining shoe is rich in 10s and Aces, the player gains a mathematical Expected Value (EV) edge over the house.
- Running Count (RC): The cumulative sum of card tag values dealt since the last shuffle.
- True Count (TC): Calculated in balanced systems as
Running Count ÷ Decks Remaining. Each +1 True Count in Hi-Lo shifts the player's advantage by approximately +0.50%. - Bet Sizing & Kelly Ramp: Advantage players bet the table minimum at neutral or negative counts (TC ≤ +1) and scale their wager upward as the True Count rises (+2 to +5+).
Comparison of Supported Card Counting Systems
| System | Type & Level | Card Values (2–6 / 7–9 / 10–A) | Best For |
|---|---|---|---|
| Hi-Lo | Balanced (Level 1) | 2–6: +1 | 7–9: 0 | 10–A: -1 | Industry standard; full Illustrious 18 & Fab 4 support |
| Ace-Five | Unbalanced (Level 1) | 5: +1 | A: -1 | Others: 0 | Beginners looking for a simple ~0.5% edge with zero deck division |
| KO (Knock-Out) | Unbalanced (Level 1) | 2–7: +1 | 8–9: 0 | 10–A: -1 | Shoe games without needing True Count division |
| Hi-Opt I & II | Balanced (Level 1 / 2) | Ace-neutral high playing efficiency | Single-deck and double-deck pitch games |
| Omega II & Zen | Balanced (Level 2) | Multi-level tags (+2 / +1 / -1 / -2) | Advanced counters maximizing both Betting & Playing Efficiency |
| Wong Halves | Balanced (Level 3) | Fractional tags (-1 to +1.5) | Highest theoretical correlation to exact computer play |
Key Illustrious 18 & Fab 4 Index Deviations (Hi-Lo)
Coined by mathematician Don Schlesinger, the Illustrious 18 and Fab 4 represent the most valuable True Count thresholds where optimal play deviates from standard Basic Strategy:
- Insurance: Take at TC ≥ +3
- 16 vs. Dealer 10: Stand at TC ≥ 0
- 15 vs. Dealer 10: Stand at TC ≥ +4
- 10,10 vs. Dealer 5: Split at TC ≥ +5
- 10,10 vs. Dealer 6: Split at TC ≥ +4
- 10 vs. Dealer 10: Double at TC ≥ +4
- 12 vs. Dealer 3: Stand at TC ≥ +2
- 12 vs. Dealer 2: Stand at TC ≥ +3
- 11 vs. Dealer A: Double at TC ≥ +1
- 9 vs. Dealer 2: Double at TC ≥ +1
- 10 vs. Dealer A: Double at TC ≥ +4
- 9 vs. Dealer 7: Double at TC ≥ +3
- 16 vs. Dealer 9: Stand at TC ≥ +5
- 13 vs. Dealer 2: Hit at TC ≤ -1
- 12 vs. Dealer 4: Hit at TC < 0
- 12 vs. Dealer 5: Hit at TC ≤ -2
- 12 vs. Dealer 6: Hit at TC ≤ -1
- 13 vs. Dealer 3: Hit at TC ≤ -2
- Fab 4 Surrender: 15 vs. 10 (TC ≥ 0), 15 vs. 9 (TC ≥ +2), 14 vs. 10 (TC ≥ +3)