How to Memorize Blackjack Index Numbers

The first time a player sees a full index chart, it looks like a second basic strategy chart layered on top of the first. Rows of hands, columns of upcards, and a number in each cell instead of a letter. That impression is the reason most people never learn indices: they try to memorize a grid, fail, and conclude the whole subject is for specialists.

It is the wrong mental model. Indices are not a chart you read. They are a short list of exceptions you carry, and the list is much shorter than the grid makes it look. Learning them is a memory problem with a known solution, and the solution is not repetition alone.

Indices are a small set, not a second chart

A basic strategy chart has to cover every hand against every upcard, because every hand comes up. An index list does not. Most cells on a strategy chart are decisions so lopsided that no realistic count flips them: you are never standing on hard 8, and you are never hitting a hard 20. Only a modest number of decisions sit close enough to the line that a shifted deck composition changes the answer.

That is what an index is. It is the true count at which a particular decision crosses over, so above the number you do one thing and below it you do the other. Our guide to index deviations covers the mechanics in detail. What matters for memorizing them is that the useful set is finite and small.

Don Schlesinger's Illustrious 18, published in Blackjack Attack, is the canonical version of that small set: the eighteen most valuable Hi-Lo deviations, ranked by how much each contributes. The ranking matters as much as the list. Value drops off steeply, so the first few plays carry a disproportionate share of what indices are worth, and learning them in order means every hour of study buys the most available.

Learn insurance before anything else

If you memorize exactly one index for the rest of your playing life, make it insurance. The Hi-Lo insurance index is about +3 true count: take insurance at +3 or higher, decline it otherwise. Basic strategy declines insurance in every situation, which our article on blackjack insurance explains, and this is the one condition under which that flips.

Insurance earns its top spot for three reasons. It is a pure bet on the composition of the remaining deck, which is exactly what a count measures, so the count maps onto it more directly than onto any playing decision. It comes up every time the dealer shows an ace, which is often. And it does not change how you play the hand, so there is no follow-on decision to get wrong.

It is also the easiest to execute. You are not recalculating a marginal hit or stand while a dealer waits. You are answering a yes or no question with a number you already hold. Get this one automatic before you touch the rest.

Group by the number, not by the hand

Here is the change that makes the rest of the list stick. Most people study indices hand by hand: what is the index for 16 against 10, what is the index for 12 against 3, and so on. That structure mirrors a strategy chart, and it is the wrong structure for recall.

At a table, you are not holding a hand and asking what its index is. You are holding a count and asking what that count changes. The count is the key you look things up by, so the memory should be organized by count. Group the plays by index value and eighteen scattered facts collapse into a handful of buckets.

Here are canonical examples from Schlesinger's published list, arranged that way. Each means: make the listed play when the true count is at or above the index, otherwise follow basic strategy.

Read it as buckets and a pattern appears. At a neutral count one decision is already live. At +1 two doubles open up. By +4 several plays land together, and they share a logic: a shoe rich in tens and aces makes standing safer, doubling into a ten more attractive, and splitting tens into a weak upcard defensible. Learning the logic of a bucket means you are not memorizing six unrelated items, you are memorizing one condition with six consequences.

A note on the two splitting entries. Splitting 10s breaks up a 20, which basic strategy never does, and our article on never splitting tens explains why it is correct at every ordinary count. These indices are also the most conspicuous plays on the list, and a player who makes them draws attention. Many counters skip them for that reason alone.

The Fab 4 belong to your game, not to a generic list

The Fab 4, also from Schlesinger, are the four most valuable late surrender deviations: 14 against 10, 15 against 10, 15 against 9 and 15 against ace. They are worth learning alongside the Illustrious 18 if the table offers late surrender, and worthless if it does not.

The catch is that their index numbers are not universal. They differ between games where the dealer stands on soft 17 and games where the dealer hits it, which our comparison of S17 and H17 covers. Memorizing a set of Fab 4 numbers off an unlabeled chart is how a player ends up confidently making the right play for a game they are not sitting at.

So before you memorize a single surrender index, establish two things: whether your table offers late surrender at all, and whether the dealer hits or stands on soft 17. Then take the numbers from a source that states which game they are for. Our article on the Fab 4 surrender deviations walks through the set. The same caution applies more broadly: indices published for a six deck shoe are not automatically the indices for a double deck game.

The quiz loop that actually works

Memorization technique matters more than study hours. Four principles carry most of the weight.

• Recognition before recall. Start by reading the list and confirming you can pick the right answer from options. Only then move to producing the number from nothing. Jumping straight to blank recall produces frustration and slow progress.
• Drill both directions. Hand to index ("16 against 10, what is the index?") and index to hand ("the count is +4, what changes?"). The second direction is the one you actually use at a table, and it is the one almost nobody practices.
• Retire nothing until it is correct cold. A play you get right during a focused study session is not learned. It is learned when you get it right a day later, with no warm up, mixed in with plays from other buckets.
• Mix indices into ordinary strategy practice. Isolated index drills teach you to expect a deviation. Real hands do not announce themselves, so the final stage is a normal hand feed where most decisions are plain basic strategy and a few are not.

Short daily sessions beat long weekly ones for this kind of material. Our daily practice routine covers how to structure them, and counting speed drills cover the prerequisite skill.

Honest perspective on what indices are worth

Indices are the last layer of counting, not the foundation, and they are frequently oversold. Most of the value in counting comes from varying bets with the count, which our article on bet spread covers. Deviations refine individual decisions at the margin and add a modest amount on top.

They also depend entirely on the layer beneath them. An index play made off a shaky count is not a refinement, it is a random deviation from correct basic strategy, and it costs more than playing the chart would have. If your running count drifts, or your true count conversion is guesswork, indices are premature. Fix the count first, with deck estimation practice if that is the weak link.

And the standard perspective applies. Counting with your head is legal in the United States, but casinos are private businesses that may refuse service, back off, or ban players they suspect of counting. No technique removes risk, no count produces guaranteed results, and losing sessions remain routine regardless of how many index numbers you can recite.

Frequently asked questions

How many blackjack index numbers do you need to memorize?

Far fewer than most people expect. The insurance index alone captures a large share of the available value, and the Illustrious 18, Don Schlesinger's published list in Blackjack Attack, covers the eighteen most valuable Hi-Lo deviations. Beyond that, extra indices add progressively less. A player who knows insurance and a dozen common plays cold is in better shape than one who half remembers fifty.

Which blackjack index should you learn first?

Insurance. The Hi-Lo insurance index is about +3 true count, meaning a counter takes insurance at +3 or higher and declines it otherwise. It is the single most valuable deviation because it is a straight side bet on deck composition, it comes up often, and it requires no change to how you play the hand itself. Learn it before any standing or doubling index.

What is the best way to memorize the Illustrious 18?

Group the plays by index value rather than by hand. Learning that stand 12 against 3 is a +2 and stand 12 against 2 is a +3 means memorizing scattered facts. Learning that a small cluster of decisions all flip at +4 turns eighteen items into a handful of buckets. Recall at the table is triggered by the count you are holding, so organize the memory the same way.

Do Fab 4 index numbers change with the table rules?

Yes. The Fab 4 are the four most valuable late surrender deviations, commonly listed as 14 against 10, 15 against 10, 15 against 9 and 15 against ace, and their index numbers differ between games where the dealer stands on soft 17 and games where the dealer hits it. Memorize the set published for the exact game you play rather than a generic list.

Are index numbers worth memorizing at all?

They add a small amount on top of a working count, not a large one. Most of the value in counting comes from varying bets with the count; deviations refine individual decisions at the margin. An index is also worthless if the count feeding it is shaky, so accurate counting comes first. No technique removes risk, and casinos are private businesses that may refuse service to suspected counters.

Keep reading

• Index Deviations Explained
• The Illustrious 18, Explained
• The Fab 4 Surrender Deviations