Editor’s note: Schlesinger’s indices assume accurate game selection inputs—always verify the rule card you are actually playing against before you trust a single DI number in the wild.

Card counting in blackjack is a deep subject. Many professionals have written about it at length. One such professional is Don Schlesinger. Not only has he written upon the subject, Schlesinger has developed card counting methods and modifications. His Desirability Index is an example of how Don Schlesinger has expanded the existing knowledge of card counting.

The Origin of the Desirability Index

January 12, 2026 · Counting Edge Editorial

Browse the explore blackjack index for related topics, or the online blackjack hub for where and how we evaluate games.

The Desirability Index in blackjack can be traced to Blackjack Attack. This book was written by Don Schlesinger many years ago, and it is still popular today. In the book, Don lays out many card counting methods. He also takes time to explain his various indices and modifications. The Desirability Index is covered in depth within the pages of Blackjack Attack. Sometimes referred to as the DI, the Desirability Index is a construct that belongs to Don Schlesinger.

He was the one to introduce the concept to the blackjack world. Other contributions of Don Schlesinger are the Illustrious 18 and Fab Four card counting indices.

What is the Blackjack DI?

The DI is a mathematical concept. It has a somewhat technical definition. The Desirability Index may be defined as a single number which is used to quantify how desirable a game of blackjack is. The number is arrived at by dividing the win rate by the standard deviation for the game in question, and then multiplying that result by 100. Obviously, you need to be in possession of certain data if you want to use the desirability index. You need to know things like the win rate and standard deviation, and that is a little more work than some card counters are willing to invest.

Indeed, some counters may not even know what these things are. Schlesinger explains them in Blackjack Attack.

The Purpose of a Desirability Index

Card counting has long been the primary way to gain an advantage when playing live blackjack. Over the years players have also learned that there are other things that can help grant an advantage. One of these is knowing which game to pick in a live casino. There are many individual blackjack games. Which one gives the card counter the best chance at a profit? The Desirability Index was developed by Schlesinger to solve that very problem.

It was created to bring things down to a single number. By comparing this one number to another, the player is able to simplify the process of choosing the right game. Other methods have also been developed over time to accomplish the same purpose, but Schlesinger would argue that these do not have the same accuracy of his methods. He could be right given his background in mathematics.

Refining How We Count Cards at Blackjack

There is no question that card counting changed the way serious players approach blackjack. Along with basic blackjack strategy, card counting is the only surefire way to establish and maintain an advantage over the house. Quite simply, you will lose in the long run unless you master both card counting and blackjack strategy. Once you become skilled in these areas you should see an improvement in your win rate. You should see an improvement in your consistency. Then, something else will happen.

You may reach a ceiling or a plateau. Getting past that plateau requires that you adopt some advanced strategies. The Desirability Index is just one example of advanced play. It is meant to be applied on top of your existing knowledge of card counting and basic strategy. DI does not replace either of those. It cannot be substituted for either of those.

It must work in tandem with them.

Is There an Advantage to DI and Advanced Blackjack Knowledge?

By now the advantage of these advanced strategies should be obvious. They have the ability to take your game to new levels. You may be able to break through the barrier that you have reached and increase your profits once more. There are many things you can learn beside the Desirability Index in blackjack. Many of Schlesinger’s other strategies are worth exploring. All you need is a willingness to keep expanding your knowledge, and you will soon see that blackjack mastery is a lifetime endeavor. The rewards keep getting better as you learn more. When you are ready to fund online practice, compare transparent bonus math in our online blackjack reviews hub—DI thinking applies to picking the rule set, not chasing a promo headline.

FAQs: Desirability Index (DI)

Does DI replace basic strategy or counting?

No—it ranks games and conditions once your counting system and strategy are already solid.

What inputs most move the DI number?

Penetration, spread constraints, rules that change win rate, and volatility from bet sizing all feed win rate and standard deviation.

Is DI useful online?

Most online RNG shoes reshuffle every hand, so traditional DI comparisons matter less than in live games with trackable slugs.

Frequently asked questions

Does DI replace basic strategy or counting?

No—DI ranks games after you already execute strategy and counting competently.

What inputs most move the DI number?

Penetration, bet spread caps, rule changes that alter win rate, and volatility from sizing all influence win rate and standard deviation.

Is DI useful online?

Less so on per-hand reshuffled RNG games; it shines when penetration and pace resemble live shoes.