Blackjack Deviation Chart (The Illustrious 18)

This page holds the full Illustrious 18 index chart — downloadable as PDF or CSV — showing exactly when the True Count justifies breaking basic strategy.

It’s written for players who already know basic strategy cold and can keep an accurate count. Not there yet? Start with our basic strategy chart and Card Counting Trainer — deviations only work on top of those two skills.

The Illustrious 18 Index Plays

Legend:
The number indicates the required True Count index to deviate from basic strategy.
S = Stand, D = Double Down, SP = Split

How to Read the Deviation Chart

Find your hand in the left column and the dealer’s upcard across the top. The cell shows the deviation play and its index — the True Count at which the deviation becomes correct.

The rule: when your True Count is equal to or greater than the index, make the deviation; below it, play basic strategy. Legend: S = Stand, D = Double Down, SP = Split.

Worked example: you hold 16 against a dealer 10. Basic strategy says hit — but the chart shows S @ 0. At any True Count of 0 or higher, you stand; at a negative count, you hit as normal.

Negative indices flip the logic’s direction, not the rule: 12 vs 5 shows S @ −2, meaning stand even in slightly negative counts — only below −2 does hitting become correct.

What Are Blackjack Deviations?

Basic strategy is the optimal way to play a neutral shoe — it assumes nothing about the cards already dealt. But once the count shifts, the remaining deck’s composition changes, and for a specific set of hands a different play becomes mathematically superior. Those plays are deviations, also called index plays.

There are two families: playing deviations (changing the move — this page) and betting deviations (raising your bet as the count climbs — covered with the fundamentals on our Card Counting Trainer page).

The Illustrious 18 — and the Fab 4

Hundreds of index plays exist, but Don Schlesinger proved you don’t need them: his Illustrious 18 are the plays that deliver the large majority of all deviation value. Beyond them, returns diminish steeply — memorizing index #40 is effort spent on pennies.

Playing a table with late surrender? Add the Fab 4 surrender indices:

• Surrender 14 vs 10 at TC +3
• Surrender 15 vs 9 at TC +2
• Surrender 15 vs 10 at TC 0
• Surrender 15 vs A at TC +1

The indices on this page assume a standard multi-deck game counted with Hi-Lo; other rule sets shift a few indices by a point.

The 18 Plays, Group by Group

The numbers are in the chart — what matters is understanding why each group works, so the logic sticks.

Insurance at True Count +3: The Most Important Deviation

Basic strategy says never take insurance — and at a neutral count that’s right. But at TC +3 or higher, the shoe is so ten-rich that the dealer’s hole card is a ten often enough to make the 2:1 payout profitable.

This single index is worth roughly a third of all deviation value. If you learn exactly one play from this page, learn this one.

Standing Deviations (16 vs 10 and the 12s)

High counts mean more tens still in the shoe — which raises your bust risk when hitting and the dealer’s bust risk when drawing. Both effects push marginal hands toward standing.

That’s why 16 vs 10 stands at TC 0, 15 vs 10 at +4, 16 vs 9 at +5, and the whole 12-versus-small-card cluster (12 vs 2 at +3, vs 3 at +2, vs 4 at 0) tightens up as the count climbs. The stiff hands you hate most are exactly where the count helps most.

Doubling Deviations (11 vs A and Friends)

A ten-rich shoe makes big doubles profitable in spots that are only marginal at a neutral count: 11 vs A doubles at +1, 10 vs 10 and 10 vs A at +4, and 9 vs 2 at +1 with 9 vs 7 at +3.

The logic mirrors the standing group: when the next card is a ten more often than usual, getting extra money out while you’re strong is worth the risk.

Splitting 10s: Profitable, but a Red Flag

10,10 vs 5 at +5 and vs 6 at +4 is mathematically correct — in a very high count against the dealer’s weakest cards, two hands starting from 10 beat one made 20.

It’s also the loudest counter tell in blackjack: recreational players never split tens, and pit staff know it. Most counters deliberately skip this play to protect their longevity — we’d advise the same. Know it exists; use it rarely, if ever.

When Do You Actually Use Deviations?

Three prerequisites, honestly stated: flawless basic strategy, an accurate running-to-true-count conversion at table speed, and a bankroll bet in line with the count. Deviations without an accurate count aren’t advanced play — they’re just mistakes with extra steps.

The recommended learning order: insurance first, then 16 vs 10 and 15 vs 10, then the rest of the 18 as your counting speed allows.

And the rule that never changes: at a neutral or unknown count, the basic strategy chart is always the answer.

How Much Are Deviations Worth?

Soberly: the full Illustrious 18 adds roughly 20–40% to a counter’s edge, depending on rules and bet spread. For a counter, that’s meaningful; for a basic-strategy player, it’s zero.

The dependency matters: most deviation value only materializes when your bet sizing already follows the count — big bets out in the high counts where deviations trigger. Cherry-picking a few index plays while flat-betting changes almost nothing except your error rate.

How to Practice Index Plays

• Drill the count in our Card Counting Trainer until converting to the True Count is automatic — indices are useless a beat too late.
• Play the free blackjack game keeping a live count, and flag every hand where an index would trigger. No money, real reps.
• Quiz from the PDF: cover the index column, name the number for each play, check, repeat.

The bar: recall any index in under a second. At a real table, hesitation is both an error and a tell.

Legality, Heat and Table Reality

Counting cards and playing indices is legal — it’s thinking, not cheating, and no jurisdiction outlaws it. But casinos are private businesses: they can shuffle up, cap your bets, or ask you to leave (“backing off”) if they suspect counting.

Unusual plays are what pits watch for — a sudden insurance bet after flat refusals, or splitting 10s, draws attention faster than bet spreads do. Play accordingly.

Online note: RNG games shuffle every hand, making counting — and therefore every index on this page — worthless there. Live-dealer shoe games vary by penetration. Real-money play is for adults 18+ (21+ in many jurisdictions) — set limits first and play responsibly.

How This Chart Was Built

The indices follow Schlesinger’s published Illustrious 18 values for a standard multi-deck Hi-Lo game, cross-checked against the simulation literature that has validated them for decades. The chart is fully consistent with our basic strategy chart and Card Counting Trainer — one system, no contradictions.

Free and donation-supported: no casino ads, no counting-course upsells, no sign-ups.

Conclusion: Master the Count First — Then Deviate

The ladder has a fixed order: basic strategy → accurate true count → the insurance index → the rest of the 18. Skipping rungs doesn’t accelerate anything; it just adds errors.

Deviations are the final few percent of a counter’s game, not a shortcut past the fundamentals. Climb at your own pace with the free tools here — and if you take it to a real table, know your limits before you know your indices. Play responsibly.