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# The Illustrious 18: Blackjack Deviations Explained
- URL: https://learnblackjack.org/illustrious-18/
- Published: 2026-10-20T00:00:00.000Z
- Updated: 2026-10-20T03:50:15.000Z
- Author: TwentyOne
- Tags: illustrious 18

The Illustrious 18 are the 18 playing deviations that earn a Hi-Lo card counter the most money. Each one swaps a basic strategy play for a different one when the true count reaches a set number, called an index. Insurance at +3 and standing on 16 against a dealer 10 at 0 are the two best known. Below you get the full list, the logic behind it, the limits nobody tells beginners, and a way to drill it.

## TL;DR

- The Illustrious 18 is a ranked list of Hi-Lo index plays, introduced by Don Schlesinger in 1986\. [Wizard of Odds](https://wizardofodds.com/games/blackjack/card-counting/high-low/?ref=learnblackjack.org) puts their share of the total index-play value at roughly 80% to 85% in a 6-deck game.
- Each play has a trigger: at or above the index you make the deviation, below it you play basic strategy (for the “stand at or above” plays).
- The published numbers assume Hi-Lo and, mainly, a multi-deck game where the dealer stands on soft 17\. Other rules and other counting systems need different indices.
- Learn basic strategy cold first. Deviations from a strategy you only half know just add errors.
- Deviations are also the most visible sign of counting at the table, so use them with judgment.

## Table of Contents

- [What the Illustrious 18 actually are](#what-the-illustrious-18-actually-are)
- [How an index number works](#how-an-index-number-works)
- [The full list, hand by hand](#the-full-list-hand-by-hand)
- [Where the 80 to 85 percent figure comes from](#where-the-80-to-85-percent-figure-comes-from)
- [Why the rules at your table change the numbers](#why-the-rules-at-your-table-change-the-numbers)
- [Deviations and casino heat](#deviations-and-casino-heat)
- [Our perspective: learn it in the right order](#our-perspective-learn-it-in-the-right-order)
- [Drilling the Illustrious 18 in TwentyOne](#drilling-the-illustrious-18-in-twentyone)
- [A practical study plan](#a-practical-study-plan)
- [FAQ](#faq)
- [Sources](#sources)

## What the Illustrious 18 actually are

Basic strategy is the best fixed play for every hand against every dealer upcard, assuming you know nothing about the cards left in the shoe. A counter does know something. When the shoe is rich in tens and aces, standing, doubling and splitting get better. When it is poor in them, hitting gets better.

So a counter plays basic strategy by default and changes a handful of decisions when the count says so. There are hundreds of possible index plays. The Illustrious 18 are the ones that move your expected profit most.

Don Schlesinger published the list in the September 1986 issue of Blackjack Forum, then covered it in depth in his book [Blackjack Attack](https://blackjackattack.com/?ref=learnblackjack.org). The name stuck because the list is short enough to memorize and valuable enough to be worth the work.

Two points are easy to miss:

- It is **not a counting system**. It sits on top of one, and that system is Hi-Lo. If you need a refresher on running count and true count, start with our [Hi-Lo card counting explainer](https://learnblackjack.org/hi-lo-card-counting-explained/).
- It is **not a set of universal rules**. The numbers come from Hi-Lo card-removal effects. As [Counting Edge’s guide to the indices](https://www.countingedge.com/blackjack-players/don-schlesinger/the-illustrious-18-card-counting-indices/?ref=learnblackjack.org) notes, they belong to the Hi-Lo framework and the rule assumptions that generated them.

## How an index number works

An index is a true count threshold. You convert your running count to a true count by dividing by the estimated decks remaining, then compare it to the index for the hand in front of you.

![Running count divided by decks leads to an index threshold](https://media.babylovegrowth.ai/blog-images/organization-59262/1792468214602_Running-count-divided-by-decks-leads-to-an-index-threshold.jpeg)

The rule for most plays is simple: **if the true count is at or above the index, make the deviation.** If it is below, play basic strategy.

Worked example with 16 against a dealer 10:

1. Basic strategy says hit (or surrender where it’s offered, which is a separate decision).
2. The index is 0.
3. Your true count is +1\. That is at or above 0, so you stand.
4. Your true count is -2\. That is below 0, so you hit.

A few indices are negative, such as standing on 12 against a 5 at -2\. Those mean you stand on 12 unless the count falls below -2, where the deck is so poor in tens that you should hit as basic strategy says. The logic is the same, just with the threshold on the negative side.

Insurance is the cleanest illustration of why this works. Under basic strategy it is a losing bet with a house edge above 7%, according to [Wizard of Odds](https://wizardofodds.com/games/blackjack/card-counting/high-low/?ref=learnblackjack.org). Insurance is really a wager that the dealer’s hole card is a ten. Once the true count reaches +3, the deck holds enough tens to make that bet profitable.

## The full list, hand by hand

The table follows the commonly published Hi-Lo ranking for a multi-deck, dealer-stands-on-soft-17 game. Cross-check your numbers against the reference at [Counting Edge](https://www.countingedge.com/blackjack-players/don-schlesinger/the-illustrious-18-card-counting-indices/?ref=learnblackjack.org) before you commit them to memory, since charts differ slightly in how they treat rounding and surrender.

| Rank | Hand vs. dealer upcard | Index (true count) | Deviation                      |
| ---- | ---------------------- | ------------------ | ------------------------------ |
| 1    | Insurance              | +3                 | Take insurance at +3 or higher |
| 2    | 16 vs. 10              | 0                  | Stand at 0 or higher           |
| 3    | 15 vs. 10              | +4                 | Stand at +4 or higher          |
| 4    | 20 vs. 5               | +5                 | Split tens at +5 or higher     |
| 5    | 20 vs. 6               | +4                 | Split tens at +4 or higher     |
| 6    | 10 vs. 10              | +4                 | Double at +4 or higher         |
| 7    | 12 vs. 3               | +2                 | Stand at +2 or higher          |
| 8    | 12 vs. 2               | +3                 | Stand at +3 or higher          |
| 9    | 11 vs. Ace             | +1                 | Double at +1 or higher         |
| 10   | 9 vs. 2                | +1                 | Double at +1 or higher         |
| 11   | 10 vs. Ace             | +4                 | Double at +4 or higher         |
| 12   | 9 vs. 7                | +3                 | Double at +3 or higher         |
| 13   | 16 vs. 9               | +5                 | Stand at +5 or higher          |
| 14   | 13 vs. 2               | \-1                | Stand at -1 or higher          |
| 15   | 12 vs. 4               | 0                  | Stand at 0 or higher           |
| 16   | 12 vs. 5               | \-2                | Stand at -2 or higher          |
| 17   | 12 vs. 6               | \-1                | Stand at -1 or higher          |
| 18   | 13 vs. 3               | \-2                | Stand at -2 or higher          |

The rank order shown is for convenience of study. Value depends on how often a situation comes up and how much the play gains, so the top few carry far more weight than the bottom few.

### Patterns that make it easier to remember

You do not have to treat 18 numbers as 18 unrelated facts.

- **Stiff hands against 2 through 6** are mostly “stand” deviations with low or negative indices. Basic strategy already stands on 13 through 16 against 2 through 6, so these plays concern the 12s and 13s on the edge.
- **Stiff hands against a 10 or 9** are the high-index stands: 16 vs. 10 at 0, 15 vs. 10 at +4, 16 vs. 9 at +5.
- **Doubles** cluster on 9, 10 and 11\. More tens left means your two-card total is more likely to land on a strong hand, so you put more money out.
- **Two splits of tens** (20 vs. 5 and 20 vs. 6) are the rarest and riskiest-looking plays. Many counters skip them in practice, a point we return to below.

## Where the 80 to 85 percent figure comes from

Wizard of Odds says that by mastering these 18 adjustments a player captures roughly [80% to 85% of the value](https://wizardofodds.com/games/blackjack/card-counting/high-low/?ref=learnblackjack.org) of all count-based playing deviations in a 6-deck game. That is the reason to stop at 18 rather than memorize 100 or more indices.

Keep the scale in perspective, though. Index plays are a supporting act. For most counters, the bulk of the edge comes from raising bets when the count is high. Deviations add to that, they do not replace it. Anyone who tells you that memorizing the list turns basic strategy into a winning game is overselling it.

## Why the rules at your table change the numbers

The published list assumes particular conditions. Counting Edge’s guidance is that indices vary by deck count, by whether the dealer hits or stands on soft 17, and by surrender availability, and that you should prefer an index set generated for your actual game over the generic list.

That has practical consequences:

- **H17 versus S17.** Many U.S. tables now hit soft 17\. Some indices shift and a few extra plays become worth knowing. Our guide to [H17 vs. S17](https://learnblackjack.org/h17-vs-s17-blackjack/) covers what changes in the basic strategy itself.
- **Single and double deck.** The indices drift further from the 6-deck numbers, and the true count conversion is different because there are fewer decks to divide by.
- **Surrender.** The Illustrious 18 does not include surrender decisions, which is why charts add the Fab 4 surrender indices as a companion set. A reader on Reddit’s blackjack forum made this exact point about a player’s 15 vs. 10 play: the list is about hit, stand, double and split, not surrender.
- **Other counting systems.** The numbers cannot be borrowed for Omega II or Zen Count without recalculation, because they depend on how Hi-Lo handles card removal.

For a wider look at which rules hurt or help the most, see our breakdown of [blackjack rule variations and house edge](https://learnblackjack.org/blackjack-rule-variations-house-edge/).

## Deviations and casino heat

A deviation is mathematically right and can still be a bad idea if it gets you barred. Stand on 16 against a 10 with no obvious reason, and an attentive floor supervisor notices. Bill Zender, a former casino executive and gaming consultant, wrote about [using the Illustrious 18 as a defensive tool](https://billzender.com/usingtheillustrious18/?ref=learnblackjack.org), and the same article is a useful reminder that these plays are among the things casino staff look for.

Experienced counters respond in different ways. Some skip the plays that look strangest, such as splitting tens, because the gain is small relative to the attention. Others use the most valuable plays, like insurance and 16 vs. 10, and accept the risk. There is no single right answer, and the choice is yours.

Counting itself is not a crime in the U.S., but casinos are private businesses and can ask you to leave. We cover where the law and casino policy sit in [Is card counting illegal?](https://learnblackjack.org/is-card-counting-illegal/). If you have a specific legal worry, such as a trespass notice you have received, talk to a licensed attorney in your state.

## Our perspective: learn it in the right order

We build a blackjack trainer, so we watch where learners stall. It is rarely the deviations themselves. It is the layer underneath.

The usual sequence of failure goes like this. Someone memorizes the Illustrious 18 table in an evening, then plays a practice shoe and gets basic strategy wrong on soft 18 or 12 against a 4\. The index plays only fire against the right base play, so one mistake in the foundation defeats the whole table. Our advice:

1. **Make basic strategy automatic** for your actual rules. Not nearly automatic, automatic. Our [basic strategy starter guide](https://learnblackjack.org/blackjack-basic-strategy/) and [memorization tips](https://learnblackjack.org/how-to-memorize-blackjack-basic-strategy/) are the place to start.
2. **Get Hi-Lo counting and true count conversion fluent** before you add any index. If you cannot keep an accurate count while dealing yourself cards, you will not apply indices correctly under pressure.
3. **Add indices in value order.** Insurance and 16 vs. 10 first, then 15 vs. 10, 10 vs. 10 and the 12s, then the rest.
4. **Practice with your real casino’s rules.** An index chart for a rule set you never play is worse than no chart.
5. **Always learn the reason**, not just the number. 12 vs. 3 at +2 makes sense once you see that the dealer busts more often when tens are plentiful and your 12 is only at risk from a ten. A rule you understand survives a long session. A rule you merely memorized does not.

That last point is why we designed our feedback around explanations rather than a bare right or wrong. If you want a drill plan that does not require a casino, see [how to practice card counting at home](https://learnblackjack.org/how-to-practice-card-counting-at-home/).

> *— Ryan*

## Drilling the Illustrious 18 in TwentyOne

TwentyOne, our iPhone blackjack trainer, gives instant feedback on every hand and explains the reasoning behind each decision. You can set the rules to match a real casino, which matters for the index issue above, and use the card counting drills and quizzes to get faster. Start with the free lessons and drills, and upgrade through the App Store if you want the premium material. You can find it on the [TwentyOne page](https://learnblackjack.org/), and the [interactive strategy chart](https://learnblackjack.org/strategy-chart/) lets you check H17, S17 and double-after-split basic strategy before you layer on deviations.

## A practical study plan

A realistic schedule for someone already solid on basic strategy and the Hi-Lo count:

- **Week 1:** Insurance at +3 and 16 vs. 10 at 0\. Drill them until the response is instant. These two come up most often.
- **Week 2:** Add 15 vs. 10, 10 vs. 10, 12 vs. 3 and 12 vs. 2.
- **Week 3:** Add the doubles (11 vs. Ace, 9 vs. 2, 10 vs. Ace, 9 vs. 7) and 16 vs. 9.
- **Week 4:** Add the negative-index 12s and 13s, then the two ten splits if you plan to use them.
- **Ongoing:** Test yourself in mixed practice at full speed, with distractions, because a casino is noisy and a living room is not.

Check your bankroll as well. Deviations do not remove variance. The [session risk of ruin calculator](https://wizardofodds.com/games/session-risk-of-ruin-calculator/?ref=learnblackjack.org) from Wizard of Odds lets you see how bankroll, hours played and hands per hour change the chance of going broke in a session.

## FAQ

### Is the Illustrious 18 only for card counters?

Yes. The indices are true count thresholds, so they only work if you are tracking the Hi-Lo count. Without a count, the right play is basic strategy every time, and that includes never taking insurance.

### Do I need to memorize all 18 to benefit?

No. The plays are not equally valuable. Insurance and 16 vs. 10 carry the most weight, so learning those first captures a good share of the benefit while you work on the rest.

### Are the indices the same for H17 and S17 games?

Not exactly. The published list is built mainly for multi-deck S17 games, and in other games some numbers are slightly off. Use an index set generated for your table’s rules when you can, and practice with those rules set up.

### What is the difference between the Illustrious 18 and the Fab 4?

The Illustrious 18 covers hit, stand, double, split and insurance decisions. The Fab 4 is a companion set of four surrender indices, so you need both if your casino offers late surrender and you want to count it.

## Sources

- [Introduction to the High-Low Card Counting Strategy, Wizard of Odds](https://wizardofodds.com/games/blackjack/card-counting/high-low/?ref=learnblackjack.org)
- [The Illustrious 18 Card Counting Indices, Counting Edge](https://www.countingedge.com/blackjack-players/don-schlesinger/the-illustrious-18-card-counting-indices/?ref=learnblackjack.org)
- [Blackjack Attack: Playing the Pros’ Way](https://blackjackattack.com/?ref=learnblackjack.org)
- [Using the Illustrious 18 as a Defensive Tool, Bill Zender and Associates](https://billzender.com/usingtheillustrious18/?ref=learnblackjack.org)
- [Session Risk of Ruin Calculator, Wizard of Odds](https://wizardofodds.com/games/session-risk-of-ruin-calculator/?ref=learnblackjack.org)

## Recommended

- [Blackjack Card Counting Deviations: Illustrious 18 Guide](https://learnblackjack.org/blackjack-card-counting-deviations)
- [Blackjack 18 vs Ace: Hit or Stand? Basic Strategy Guide](https://learnblackjack.org/blackjack-18-vs-ace)
- [Blackjack 18 vs 9: Hit or Stand? Basic Strategy Guide](https://learnblackjack.org/blackjack-18-vs-9)
- [Blackjack 18 vs 10: Hit or Stand? Basic Strategy Guide](https://learnblackjack.org/blackjack-18-vs-10)

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