The Hi Lo skill refers to the Hi-Lo card counting system used in blackjack. It is a technique where players assign point values (+1, 0, or −1) to every card dealt, track a running total, and use that information to place larger bets when the remaining deck favours them. It was invented by mathematician Harvey Dubner in 1963 and later refined by Edward Thorp.
You've probably heard the phrase "counting cards" and imagined someone like Rain Man sat silently in a tuxedo, memorising every card on the table. The reality? Much simpler — and far more interesting. The Hi Lo skill is all about basic arithmetic and staying calm under pressure. No photographic memory required.
Whether you found this term in a blackjack forum, a strategy guide, or a casual conversation — this article explains everything clearly. We'll cover what it means, how it works step-by-step, what the numbers actually say, and whether it's genuinely worth learning.
What Is the Hi Lo System in Blackjack?
Hi Lo (also written as High-Low or Hi-Low) is the most popular card counting strategy in blackjack. It is a technique that assigns a value to each card dealt, helping players track the ratio of high cards to low cards remaining in the deck.
The logic behind it is elegant. Card counting is based on statistical evidence that high cards — aces, 10s — benefit the player, while low cards — 2s through 6s — benefit the dealer. So if you know more high cards are left in the shoe, you bet bigger. Simple as that.
The Hi-Lo card counting strategy was created by Harvey Dubner in 1963 and later refined by famous blackjack pros and authors like Stanford Wong and Edward Thorp. It forms the backbone of Professional Blackjack, a Stanford Wong book often called the "card counting bible."
The Hi Lo Card Values: The Foundation of the Skill
This is where the "skill" part begins. Every card that hits the table gets a tag. You add or subtract from your mental count based on what you see. Here is the full card value table used in the Hi Lo system:
| Card(s) | Hi Lo Value | Why It Matters | Effect on Player |
|---|---|---|---|
| 2, 3, 4, 5, 6 | +1 (Low Cards) | Bad for player — dealer loves these | Count goes up → deck improving |
| 7, 8, 9 | 0 (Neutral) | No significant effect either way | Count stays the same |
| 10, J, Q, K, Ace | −1 (High Cards) | Great for player — increases blackjack odds | Count goes down → deck weakening |
Source: Wizard of Odds — High-Low Card Counting Strategy
This is a balanced system. When you start your count at 0, you should end at 0 when every card has been seen and the deck needs to be shuffled. That symmetry is what makes it reliable.
How to Use the Hi Lo Skill: Step-by-Step
The process has three main stages. Master these three, and you understand Hi Lo completely.
Start at zero. Add or subtract 1 for every card you see on the table — yours, the dealer's, and other players'. Do this continuously and silently throughout the game.
Divide the running count by the number of decks remaining to get what is known as the "True Count." You don't need to be exact — a rough estimate is fine. For example: running count of +7, four decks left → True Count = 1.75, round to 2.
Increase your bet size when the true count is high — indicating a deck rich in high cards — and decrease it when the true count is low. Bet big when the odds tilt your way. Bet small when they don't.
🃏 Real Example: Running Count in Action
Cards dealt in order: 3, 5, K, 7, Q, A, 8, 5, 4, 2
- 3 → +1 | 5 → +1 | K → −1 | 7 → 0 | Q → −1
- A → −1 | 8 → 0 | 5 → +1 | 4 → +1 | 2 → +1
- Running Count = +2
Two decks remain → True Count = +2 ÷ 2 = +1. The player now has a slight edge.
Source: Wizard of Odds
Why the Hi Lo Skill Actually Works: The Statistics
This isn't guesswork. There is real data behind this system. A simulation running over 500 million hands shows a strong relationship between the true count and player advantage. When no card counting system is used — basic strategy alone — the player has a −0.35% advantage.
In most cases, the advantage from Hi Lo will range from 0.5% to 1.2%. This may not sound like much, but it is actually a fairly significant edge — often more than the advantage the house has when you simply play with basic strategy.
📊 Player Advantage by True Count (Hi Lo System)
Data based on 500M+ hand simulations. Source: Stanford Blackjack Research · 2 decks, 75% penetration
A true count of +2 puts the player advantage up to about half of 1 percent, and the house edge becomes the player's edge. A true count of +3 makes a player advantage of roughly 1%.
Hi Lo vs. Other Card Counting Systems
There are several card counting systems out there. Hi Lo is far from the only option — but it is the most popular for good reason. Here is how the major systems compare:
| System | Difficulty | Accuracy | Best For | Balanced? |
|---|---|---|---|---|
| Hi Lo ⭐ | Beginner | Very Good | All players | Yes |
| KO (Knockout) | Beginner | Good | Beginners | No (unbalanced) |
| Omega II | Advanced | Excellent | Expert players | Yes |
| Wong Halves | Expert | Excellent | Expert players | Yes |
| Thorp Ultimate | Expert | Highest | Professional teams | Yes |
Sources: Casino.us · Gambling Nerd
Hi Lo is the easiest to learn and perfect, but there are more accurate counting systems. Omega II, Wong Halves, and Thorp Ultimate are more accurate, but they are also complicated and harder to perfect. Accuracy means nothing if you can't execute under pressure.
When it comes to blackjack card counting, simpler is better. The key is accuracy rather than using a highly complicated system that increases the likelihood of mistakes. Blackjack legends like Al Francesco and Tommy Hyland made fortunes using Hi Lo — not some obscure advanced formula.
What Makes Hi Lo a "Skill" — And Not Just Luck?
This is the key question. And it's a fair one. If it's just adding and subtracting, where does the skill come in?
- Mental stamina under distraction: Casinos are deliberately loud, busy, and distracting. Keeping an accurate running count while chatting, drinking, and watching multiple hands takes serious focus.
- Camouflage behaviour: For successful card counters, skill at "cover" behaviour — hiding the counting and avoiding drawing suspicion from casino staff — may be just as important as playing skill.
- Bet spreading correctly: Knowing when and how much to raise bets without triggering casino red flags is its own skill. Casinos look out for players shifting between low and high bets when the true count changes.
- Playing deviations: For some hands, you will play according to the True Count and a table of "Index Numbers," rather than basic strategy. For example, a player 15 against a dealer 10 should stand if the True Count is +4 or higher, otherwise hit.
- Bankroll discipline: Knowing when not to bet big is often harder than knowing when to do so.
Put simply — anyone can learn the card values in 10 minutes. Mastering the full Hi Lo skill takes weeks of disciplined practice.
How to Practice the Hi Lo Skill: A Practical Guide
Where to Start
- Learn the three card groups and their values by heart (under 30 minutes)
- Deal cards to yourself from a standard deck and keep the running count
- Practice until you can flip through a full 52-card deck in under 30 seconds accurately
- Add a distraction — music, TV, conversation — and repeat
- Move to multi-deck practice (shuffle 6 decks together)
- Practice converting running count → true count on the fly
Practice Methods at a Glance
| Practice Method | Best For | Cost | Difficulty |
|---|---|---|---|
| Deal cards solo at home | Beginners building speed | Free | Easy |
| Friend acting as dealer | Realistic pace training | Free | Medium |
| Online card counting trainer | Accuracy testing | Free / Low cost | Medium |
| Low-stakes live casino play | Real environment practice | Low risk | Hard |
| Counting while watching TV | Distraction tolerance | Free | Hard |
Limitations of the Hi Lo System: What You Should Know
Hi Lo is powerful — but it isn't magic. There are real limits to how much it helps. You need to know these before heading to any casino.
- Continuous Shuffle Machines (CSMs): These shuffle the deck constantly. Card counting is useless against them. Online casinos employ random number generators, making it impossible to track specific cards.
- Deep penetration matters: Regular shuffles and randomisation can ruin your chances of card counting. The less of the shoe that is dealt before a reshuffle, the weaker your edge.
- More decks = harder: The total number of decks the casino uses can affect your odds — the more decks there are, the higher the house edge and the harder card counting becomes.
- Variance is real: With a session length of 50 rounds, a counter wins only 52% of sessions. With 500 rounds, that rises to 56%. You need a large bankroll and patience.
- Casino countermeasures: Many casino chains keep databases of players they consider undesirable. If a player is found in such a database, they will almost certainly be banned from play.
Card counting is not illegal in most jurisdictions. However, casinos are private property and can ask you to leave if they suspect it. Always know the rules of the venue you are playing in.
Hi Lo Skill: Key Facts Summary
| Fact | Detail |
|---|---|
| Full Name | Hi-Lo Card Counting System (also: High-Low, Plus-Minus) |
| Invented By | Harvey Dubner (1963), refined by Edward Thorp & Stanford Wong |
| Skill Level Required | Beginner to Intermediate |
| System Type | Balanced, Level 1 counting system |
| House Edge Reduction | Can shift from −0.35% to +0.5% → +1.5%+ advantage |
| Works Online? | No (RNG games). Yes (live dealer blackjack, with limits) |
| Time to Learn Basics | 1–3 hours for values; weeks for full proficiency |
| Famously Used By | The MIT Blackjack Team (film: 21) |
Sources: Wikipedia — Card Counting · Wizard of Odds
Frequently Asked Questions
Is Hi Lo card counting illegal?
No. Card counting is not illegal in most countries. It uses no devices and involves only mental arithmetic. However, casinos may ask you to leave or restrict your play if they detect it, as it is within their rights as private venues.
Does Hi Lo work in online blackjack?
It is not possible to count cards in virtual RNG blackjack games, where the RNG effectively "shuffles" the cards after every hand. It can work in some live dealer games if the shoe is dealt deeply enough before reshuffling.
How long does it take to master Hi Lo?
Most people learn the card values in under an hour. Accurate, fast counting under real casino conditions typically takes several weeks of consistent daily practice. Team play adds another layer of coordination training.
Do you need to memorise every card?
Card counters do not need unusual mental abilities — they do not track or memorise specific cards. The system only tracks whether the deck is getting richer or poorer in high-value cards. That's it.
What is the difference between running count and true count?
The running count is the raw ongoing total of your card tags. The true count adjusts for how many decks remain — it is the running count divided by remaining decks. Having a +5 running count with 6 decks remaining is a completely different scenario from having a +5 running count with only 1 deck remaining.
What is the MIT Blackjack Team connection?
The MIT Blackjack Team used a system where spotters would sit at tables playing minimum bets while keeping a count, then signal a "big player" to join when the count was high. This was the inspiration for the Hollywood film 21.
Final Word
The Hi Lo skill is not a cheat code. It doesn't guarantee winnings in any single session. What it does is tilt the mathematical odds ever so slightly in your favour over a long period of play — and in a game where the house normally wins, that shift is genuinely significant.
Think of it this way: the casino relies on you not thinking carefully. The Hi Lo system is simply thinking carefully — with a very simple set of rules.
Start with the basics, practice until counting is second nature, and never underestimate the importance of looking like you're just having a good time at the table. That last part, as it turns out, might be the hardest skill of all.
The Hi Lo skill refers to the Hi-Lo card counting system used in blackjack. It is a technique where players assign point values (+1, 0, or −1) to every card dealt, track a running total, and use that information to place larger bets when the remaining deck favours them. It was invented by mathematician Harvey Dubner in 1963 and later refined by Edward Thorp.
You've probably heard the phrase "counting cards" and imagined someone like Rain Man sat silently in a tuxedo, memorising every card on the table. The reality? Much simpler — and far more interesting. The Hi Lo skill is all about basic arithmetic and staying calm under pressure. No photographic memory required.
Whether you found this term in a blackjack forum, a strategy guide, or a casual conversation — this article explains everything clearly. We'll cover what it means, how it works step-by-step, what the numbers actually say, and whether it's genuinely worth learning.
What Is the Hi Lo System in Blackjack?
Hi Lo (also written as High-Low or Hi-Low) is the most popular card counting strategy in blackjack. It is a technique that assigns a value to each card dealt, helping players track the ratio of high cards to low cards remaining in the deck.
The logic behind it is elegant. Card counting is based on statistical evidence that high cards — aces, 10s — benefit the player, while low cards — 2s through 6s — benefit the dealer. So if you know more high cards are left in the shoe, you bet bigger. Simple as that.
The Hi-Lo card counting strategy was created by Harvey Dubner in 1963 and later refined by famous blackjack pros and authors like Stanford Wong and Edward Thorp. It forms the backbone of Professional Blackjack, a Stanford Wong book often called the "card counting bible."
The Hi Lo Card Values: The Foundation of the Skill
This is where the "skill" part begins. Every card that hits the table gets a tag. You add or subtract from your mental count based on what you see. Here is the full card value table used in the Hi Lo system:
| Card(s) | Hi Lo Value | Why It Matters | Effect on Player |
|---|---|---|---|
| 2, 3, 4, 5, 6 | +1 (Low Cards) | Bad for player — dealer loves these | Count goes up → deck improving |
| 7, 8, 9 | 0 (Neutral) | No significant effect either way | Count stays the same |
| 10, J, Q, K, Ace | −1 (High Cards) | Great for player — increases blackjack odds | Count goes down → deck weakening |
Source: Wizard of Odds — High-Low Card Counting Strategy
This is a balanced system. When you start your count at 0, you should end at 0 when every card has been seen and the deck needs to be shuffled. That symmetry is what makes it reliable.
How to Use the Hi Lo Skill: Step-by-Step
The process has three main stages. Master these three, and you understand Hi Lo completely.
Start at zero. Add or subtract 1 for every card you see on the table — yours, the dealer's, and other players'. Do this continuously and silently throughout the game.
Divide the running count by the number of decks remaining to get what is known as the "True Count." You don't need to be exact — a rough estimate is fine. For example: running count of +7, four decks left → True Count = 1.75, round to 2.
Increase your bet size when the true count is high — indicating a deck rich in high cards — and decrease it when the true count is low. Bet big when the odds tilt your way. Bet small when they don't.
🃏 Real Example: Running Count in Action
Cards dealt in order: 3, 5, K, 7, Q, A, 8, 5, 4, 2
- 3 → +1 | 5 → +1 | K → −1 | 7 → 0 | Q → −1
- A → −1 | 8 → 0 | 5 → +1 | 4 → +1 | 2 → +1
- Running Count = +2
Two decks remain → True Count = +2 ÷ 2 = +1. The player now has a slight edge.
Source: Wizard of Odds
Why the Hi Lo Skill Actually Works: The Statistics
This isn't guesswork. There is real data behind this system. A simulation running over 500 million hands shows a strong relationship between the true count and player advantage. When no card counting system is used — basic strategy alone — the player has a −0.35% advantage.
In most cases, the advantage from Hi Lo will range from 0.5% to 1.2%. This may not sound like much, but it is actually a fairly significant edge — often more than the advantage the house has when you simply play with basic strategy.
📊 Player Advantage by True Count (Hi Lo System)
Data based on 500M+ hand simulations. Source: Stanford Blackjack Research · 2 decks, 75% penetration
A true count of +2 puts the player advantage up to about half of 1 percent, and the house edge becomes the player's edge. A true count of +3 makes a player advantage of roughly 1%.
Hi Lo vs. Other Card Counting Systems
There are several card counting systems out there. Hi Lo is far from the only option — but it is the most popular for good reason. Here is how the major systems compare:
| System | Difficulty | Accuracy | Best For | Balanced? |
|---|---|---|---|---|
| Hi Lo ⭐ | Beginner | Very Good | All players | Yes |
| KO (Knockout) | Beginner | Good | Beginners | No (unbalanced) |
| Omega II | Advanced | Excellent | Expert players | Yes |
| Wong Halves | Expert | Excellent | Expert players | Yes |
| Thorp Ultimate | Expert | Highest | Professional teams | Yes |
Sources: Casino.us · Gambling Nerd
Hi Lo is the easiest to learn and perfect, but there are more accurate counting systems. Omega II, Wong Halves, and Thorp Ultimate are more accurate, but they are also complicated and harder to perfect. Accuracy means nothing if you can't execute under pressure.
When it comes to blackjack card counting, simpler is better. The key is accuracy rather than using a highly complicated system that increases the likelihood of mistakes. Blackjack legends like Al Francesco and Tommy Hyland made fortunes using Hi Lo — not some obscure advanced formula.
What Makes Hi Lo a "Skill" — And Not Just Luck?
This is the key question. And it's a fair one. If it's just adding and subtracting, where does the skill come in?
- Mental stamina under distraction: Casinos are deliberately loud, busy, and distracting. Keeping an accurate running count while chatting, drinking, and watching multiple hands takes serious focus.
- Camouflage behaviour: For successful card counters, skill at "cover" behaviour — hiding the counting and avoiding drawing suspicion from casino staff — may be just as important as playing skill.
- Bet spreading correctly: Knowing when and how much to raise bets without triggering casino red flags is its own skill. Casinos look out for players shifting between low and high bets when the true count changes.
- Playing deviations: For some hands, you will play according to the True Count and a table of "Index Numbers," rather than basic strategy. For example, a player 15 against a dealer 10 should stand if the True Count is +4 or higher, otherwise hit.
- Bankroll discipline: Knowing when not to bet big is often harder than knowing when to do so.
Put simply — anyone can learn the card values in 10 minutes. Mastering the full Hi Lo skill takes weeks of disciplined practice.
How to Practice the Hi Lo Skill: A Practical Guide
Where to Start
- Learn the three card groups and their values by heart (under 30 minutes)
- Deal cards to yourself from a standard deck and keep the running count
- Practice until you can flip through a full 52-card deck in under 30 seconds accurately
- Add a distraction — music, TV, conversation — and repeat
- Move to multi-deck practice (shuffle 6 decks together)
- Practice converting running count → true count on the fly
Practice Methods at a Glance
| Practice Method | Best For | Cost | Difficulty |
|---|---|---|---|
| Deal cards solo at home | Beginners building speed | Free | Easy |
| Friend acting as dealer | Realistic pace training | Free | Medium |
| Online card counting trainer | Accuracy testing | Free / Low cost | Medium |
| Low-stakes live casino play | Real environment practice | Low risk | Hard |
| Counting while watching TV | Distraction tolerance | Free | Hard |
Limitations of the Hi Lo System: What You Should Know
Hi Lo is powerful — but it isn't magic. There are real limits to how much it helps. You need to know these before heading to any casino.
- Continuous Shuffle Machines (CSMs): These shuffle the deck constantly. Card counting is useless against them. Online casinos employ random number generators, making it impossible to track specific cards.
- Deep penetration matters: Regular shuffles and randomisation can ruin your chances of card counting. The less of the shoe that is dealt before a reshuffle, the weaker your edge.
- More decks = harder: The total number of decks the casino uses can affect your odds — the more decks there are, the higher the house edge and the harder card counting becomes.
- Variance is real: With a session length of 50 rounds, a counter wins only 52% of sessions. With 500 rounds, that rises to 56%. You need a large bankroll and patience.
- Casino countermeasures: Many casino chains keep databases of players they consider undesirable. If a player is found in such a database, they will almost certainly be banned from play.
Card counting is not illegal in most jurisdictions. However, casinos are private property and can ask you to leave if they suspect it. Always know the rules of the venue you are playing in.
Hi Lo Skill: Key Facts Summary
| Fact | Detail |
|---|---|
| Full Name | Hi-Lo Card Counting System (also: High-Low, Plus-Minus) |
| Invented By | Harvey Dubner (1963), refined by Edward Thorp & Stanford Wong |
| Skill Level Required | Beginner to Intermediate |
| System Type | Balanced, Level 1 counting system |
| House Edge Reduction | Can shift from −0.35% to +0.5% → +1.5%+ advantage |
| Works Online? | No (RNG games). Yes (live dealer blackjack, with limits) |
| Time to Learn Basics | 1–3 hours for values; weeks for full proficiency |
| Famously Used By | The MIT Blackjack Team (film: 21) |
Sources: Wikipedia — Card Counting · Wizard of Odds
Frequently Asked Questions
Is Hi Lo card counting illegal?
No. Card counting is not illegal in most countries. It uses no devices and involves only mental arithmetic. However, casinos may ask you to leave or restrict your play if they detect it, as it is within their rights as private venues.
Does Hi Lo work in online blackjack?
It is not possible to count cards in virtual RNG blackjack games, where the RNG effectively "shuffles" the cards after every hand. It can work in some live dealer games if the shoe is dealt deeply enough before reshuffling.
How long does it take to master Hi Lo?
Most people learn the card values in under an hour. Accurate, fast counting under real casino conditions typically takes several weeks of consistent daily practice. Team play adds another layer of coordination training.
Do you need to memorise every card?
Card counters do not need unusual mental abilities — they do not track or memorise specific cards. The system only tracks whether the deck is getting richer or poorer in high-value cards. That's it.
What is the difference between running count and true count?
The running count is the raw ongoing total of your card tags. The true count adjusts for how many decks remain — it is the running count divided by remaining decks. Having a +5 running count with 6 decks remaining is a completely different scenario from having a +5 running count with only 1 deck remaining.
What is the MIT Blackjack Team connection?
The MIT Blackjack Team used a system where spotters would sit at tables playing minimum bets while keeping a count, then signal a "big player" to join when the count was high. This was the inspiration for the Hollywood film 21.
Final Word
The Hi Lo skill is not a cheat code. It doesn't guarantee winnings in any single session. What it does is tilt the mathematical odds ever so slightly in your favour over a long period of play — and in a game where the house normally wins, that shift is genuinely significant.
Think of it this way: the casino relies on you not thinking carefully. The Hi Lo system is simply thinking carefully — with a very simple set of rules.
Start with the basics, practice until counting is second nature, and never underestimate the importance of looking like you're just having a good time at the table. That last part, as it turns out, might be the hardest skill of all.
