Hi-Lo System

Hi-Lo System

The Hi-Lo system for counting cards in blackjack is one of the most venerable advantage strategies in the casino. When most people who know anything about card counting discuss the subject, they're talking about this specific system. It's easily understood, effective, and effective. If you've read any kind of scholarly or mathematical analysis of how and why counting gets an edge over the casino, chances are good that the study used the Hi-Lo System for analysis purposes.

According to Norm Wattenberger at QFIT, the strategy was originally created by Harvey Dubner in 1963. Julian Braun made some refinements, then Edward Thorp published the system in his book Beat the Dealer (which is considered by many to be the first card counting book.) It was then further refined by Stanford Wong and published again in the book Professional Blackjack.

How to Count Cards Using the Hi-Lo System

We wrote extensively about card counting in general on our main card counting page, but in brief, here's how it works:

Card counters track the ratio of high cards to low cards left in the deck so that they can raise their bets when the odds are in their favor. When a deck has a relatively high number of aces and 10 cards in it, you're more likely to be dealt a blackjack (or a "natural") and receive the 3 to 2 payout. If you don't understand why this works, try a little thought experiment:

Take a deck of cards, and remove all the cards that aren't aces or 10s. Do you think you'd be more likely to be dealt a blackjack with that deck? Of course you would, and the reasons are obvious.

But the reality is that every card dealt out of the deck affects those odds. If you can keep a rough estimate going of that ratio, you'll know when to raise your bets and by how much.

So every card in the Hi-Lo System is assigned a value, and as you see each card, you add or subtract that value in order to maintain a running count.

Here's the value assigned to each card in this system:

  • Aces and 10s are worth -1.
  • 2s, 3s, 4s, 5s, and 6s are worth +1.
  • 7s, 8s, and 9s are wordth 0.

You might notice that there are 20 cards worth +1 (4 of each rank.) There are also 20 cards worth -1. (4 aces, 4 jacks, 4 queens, 4 kings, and 4 10s.) Since the cards are assigned values of +1 and -1, and since there are the same number of cards of each value, this is called a "balanced count". If you count through an entire deck of cards using this system, you'll end up with a total of 0. That's true of any balanced counting system.

You'll also notice that you're only required to add 1 or subtract 1. There aren't cards worth 2 points or 3 points. This is what card counting experts call a "single level" system. More complicated card counting systems will sometimes assign different scores to different cards. We know of one system that assigns half points to some cards.

The goals of these unbalanced and multi-level systems are to increase the accuracy with which you can gauge your edge against the casino, so you can make more appropriately sized bets. They also provide you with more accurate information you can use to adjust your strategy decisions based on the count.

The goal of the Hi-Lo System is to be a practical, easily-learned system that still provides the counter with an edge over the casino. In this respect, it works admirably.

Converting the Running Count Into a True Count

If you're playing in a single deck blackjack game, you don't have to worry about this. Your running count is a more-or-less accurate representation of how good or bad the deck is.

But not all games are single deck games.

In fact, most games use 6 or 8 decks.

Since there are so many more cards in a pack with multiple decks in it, the effect of each card that's dealt is diluted.

Here's why:

If an ace is dealt out of a single 52 card deck, you only have 3 aces left. That's a significant change.

But if an ace is dealt out of a pack of cards using 8 decks, you have 31 aces left in the deck. That's a change, but it's not nearly as significant.

To take into account this dilutive effect, you take the running count and divide it by the number of decks left in the shoe.

This is a skill you'll need to practice, too—estimating the number of decks left in the shoe.

Our Advice

The only way to get good at this is to practice, and we suggest practicing at home rather than practicing at the casino when real money is on the line.

Bet Sizing Using the Hi-Lo System

Most of the edge to be gained from using the Hi-Lo System comes from sizing your bets. To do this, you decide on a betting range in units before sitting down to play. We've seen recommendations that you range your bets from 1 unit to 4 units, but we've also seen recommendations that you be willing to bet up to 10 units.

The reason for using a more conservative max bet is to reduce the chance of getting heat from the casino. Pit bosses and dealers are aware of how card counting works, and when they see a player ranging her bets wildly, they start watching to see if you're counting. If they think you're counting, they'll start shuffling every hand. Or they might even ask you to not play blackjack or even leave the casino entirely.

At any rate, you size your bet based on the true count, not the running count. You start with a single unit, then multiply that by the true count to get your bet size. But you never go over whatever max you've decided on beforehand, regardless of the count.

  • If the count is negative, 0, or 1, you'll flat bet with your minimum bet.
  • If the count is +2, you'll double that bet size.
  • If it's +3, you'll triple that bet size.

An so on.

If your betting unit is $100 per hand, you're looking at betting $200 when the count is +2, $300 when the count is +3, and so on.

This single change to your playing strategy will give you an edge over the house, assuming that you're already playing with basic strategy and not making any other changes.

In fact, this system is excellent at determining when you should raise your bets and by how much. According to QFIT, the betting correlation for this system is 0.97. (1 would be perfect.) It's hard to get much better than that.

On the other hand, some card counters also like to get an edge by adjusting their basic strategy decisions based on the count. The Hi-Lo System is significantly less effective for this purpose, with a playing efficiency score of only 0.51.


The Hi-Lo System is probably the easiest and most common card counting system in use, and it's perfect for beginners. If you decide you want to try counting cards, the Hi-Lo System is probably the best place to start.

You get an edge with a simple method of calculating the approximate ratio of high cards to low cards in the deck. All you have to do is add 1 and subtract 1 at the appropriate times.

Then you convert that running count into a true count. The true count is what determines how much you should bet per hand. The increased likelihood of having more money in action when you have a better chance of getting dealt a blackjack and the corresponding 3 to 2 payout is where you get your edge.

The Hi-Lo System isn't the best for informing changes to your basic strategy decisions, but that's not where most of your edge comes from anyway. Even experienced advantage gamblers like David Sklansky recommend using the Hi-Lo System for counting cards in blackjack.



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