The Fab 4 are the four most important surrender deviations for games offering Late Surrender: surrender 15 vs 10 at TC ≥ 0, surrender 15 vs 9 at TC ≥ +2, surrender 15 vs Ace at TC ≥ +1, and surrender 14 vs 10 at TC ≥ +3. If your casino offers Late Surrender, memorizing these four indices is more valuable than learning the bottom half of the Illustrious 18.

Why should I split tens against a dealer 5 or 6?

At TC +5 or higher, the shoe is so rich in high cards that splitting tens becomes mathematically profitable — each ten becomes the start of a strong hand, and the dealer is very likely to bust. However, this play is an obvious signal to casino staff that you are counting cards. Most professional counters avoid it entirely to preserve table longevity. The calculator includes a 'Hide High Heat' option for this reason.

How much do deviations add to a card counter's edge?

Playing deviations account for approximately 20-30% of a card counter's total advantage. The other 70-80% comes from bet variation (betting more at high counts). A counter using only bet variation with no play deviations might earn 60-80% of the theoretical win rate. Adding the Illustrious 18 captures most of the remaining value. The marginal gain from memorizing deviations beyond the I18 is very small.

Blackjack Deviations Calculator: Illustrious 18 & Fab 4 Charts

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Basic strategy reduces the house edge to roughly 0.5%, but it cannot flip the odds. To gain an edge over the casino, you need two things: a True Count and the knowledge of when that count justifies breaking the standard rules. These breaks are called deviations.

This calculator replaces static charts with a dynamic tool. Enter your current True Count and table rules, and it highlights exactly which deviations are active right now — showing you when to stand on 16, double 10 vs Ace, or take insurance.

Blackjack Deviations

Illustrious 18 + Fab 4

Current True Count (TC)

Surrender (LS)

Not Allowed

Allowed (Fab 4)

Dealer Rules

Stand Soft 17

Hit Soft 17

Hide High Heat (Split 10s)

Player Hand	Dealer Up	Index (TC)	Basic Strategy	Deviation

How to Use the Calculator

Enter Current True Count: Use the +/− buttons. If you need to compute it first, use the True Count Calculator.
Configure Table Rules: Toggle Surrender on to see the Fab 4 surrender indices. Select S17 or H17 based on the table felt.
Manage Heat: Check “Hide High Heat” to exclude plays like splitting tens that alert pit bosses to counting.
Read the Chart: Green-highlighted rows are active deviations — these override basic strategy at the current count. The “Deviation” column shows the correct play.

Note on S17/H17: Index numbers shown are based on S17 rules. Under H17, 1-2 indices may shift by ±1 (most notably, 11 vs Ace is already a basic strategy double under H17 and doesn’t need a deviation). For most practical purposes, the S17 indices work for both rule sets.

The Illustrious 18: Complete Reference

Don Schlesinger ranked all blackjack playing deviations by expected value gain. The top 18 — the “Illustrious 18” — capture roughly 80-85% of the total gain available from play variations. Here is the complete list, ranked by value:

#	Player Hand	Dealer	Index	Basic Strategy	Deviation	Rule
1	Insurance	Ace	≥ +3	Pass	Buy Insurance	TC ≥ index
2	16	10	≥ 0	Hit	Stand	TC ≥ index
3	15	10	≥ +4	Hit	Stand	TC ≥ index
4	10,10	5	≥ +5	Stand	Split 🔥	TC ≥ index
5	10,10	6	≥ +4	Stand	Split 🔥	TC ≥ index
6	10 (total)	10	≥ +4	Hit	Double	TC ≥ index
7	12	3	≥ +2	Hit	Stand	TC ≥ index
8	12	2	≥ +3	Hit	Stand	TC ≥ index
9	11	Ace	≥ +1	Hit	Double	S17 only
10	9	2	≥ +1	Hit	Double	TC ≥ index
11	10 (total)	Ace	≥ +4	Hit	Double	TC ≥ index
12	9	7	≥ +3	Hit	Double	TC ≥ index
13	16	9	≥ +5	Hit	Stand	TC ≥ index
14	13	2	< −1	Stand	Hit	TC < index
15	12	4	< 0	Stand	Hit	TC < index
16	12	5	< −2	Stand	Hit	TC < index
17	12	6	< −1	Stand	Hit	TC < index
18	13	3	< −2	Stand	Hit	TC < index

🔥 = High Heat play (draws pit boss attention). Items 14-18 are “negative correlation” deviations — you deviate to hitting when the count drops below the index, because a low count means the shoe is poor in 10s and standing on stiffs is less justified.

How Deviations Work: Two Types

Understanding the logic behind deviations matters more than memorizing numbers. There are two types:

Positive correlation (items 1-13): These activate when TC ≥ the index. A high count means more 10s remain, which makes standing on stiffs safer (dealer more likely to bust), doubling on good totals more profitable (more 10s to catch), and insurance profitable (more 10s for the dealer’s hole card).

Negative correlation (items 14-18): These activate when TC < the index. A low count means fewer 10s remain, which makes standing on 12 or 13 against weak dealer cards less justified — hitting becomes safer because there are fewer 10s to bust you.

The Decision EV Calculator shows the exact expected value of each action. Deviations are the points where the EV ranking flips between two actions as the count changes.

Real-World Examples

Example 1: Insurance (Deviation #1)

Dealer shows an Ace at TC +3. Basic strategy says never take insurance — but at TC +3, roughly 33% or more of the remaining cards are 10-valued. Insurance pays 2:1, and the breakeven point is 33.3%, so it becomes a +EV bet. This single deviation is worth more than all other play variations combined.

Example 2: Standing on 16 vs 10 (Deviation #2)

At TC ≥ 0, the shoe has at least a neutral ratio of high cards. Hitting 16 means roughly 62% chance of busting. Standing gives you a chance the dealer busts too. At TC 0, the EV of standing approximately equals the EV of hitting. Above TC 0, standing becomes increasingly correct.

Example 3: Hitting 12 vs 4 (Deviation #15)

At TC < 0 (negative count), the shoe is depleted of 10s. Basic strategy says stand on 12 vs 4 because the dealer might bust — but in a low count, the dealer is less likely to bust and your 12 is more likely to improve safely. Hit instead.

The Fab 4: Surrender Deviations

If your casino offers Late Surrender, these four indices save half your bet in specific bad situations. Enable “Allowed (Fab 4)” in the calculator to see them.

15 vs 10 (TC ≥ 0): Even at a neutral count, surrendering saves more than hitting. This is the most valuable surrender deviation. 15 vs Ace (TC ≥ +1): The Ace up-card is dangerous; surrender early. 15 vs 9 (TC ≥ +2): The 9 makes a 19, which beats your likely outcomes. 14 vs 10 (TC ≥ +3): Your 14 is terrible against a probable 20.

When surrender is available, the Fab 4 are worth more than learning Illustrious 18 entries #10-18 combined. Use the House Edge Calculator to see how surrender affects overall edge, and the Penetration Calculator to determine whether the game is worth counting in the first place.

Related Blackjack Tools

True Count Calculator — Convert running count to true count
Card Counting Guide — Complete Hi-Lo system walkthrough
Basic Strategy Calculator — The baseline plays these deviations modify
Decision EV Calculator — Exact EV for each action (shows why deviations trigger)
House Edge Calculator — Base edge by rules (determines your starting disadvantage)
Penetration Calculator — Is the game worth counting?
Bankroll Calculator — Risk of Ruin with your edge and spread
Variance Calculator — SD and N0 for counting with deviations

Frequently Asked Questions (FAQ)

What are the Illustrious 18?

The 18 most valuable playing deviations from basic strategy, ranked by Don Schlesinger in Blackjack Attack. They capture roughly 80-85% of the total gain available from play variations. Insurance at TC ≥ +3 is the single most valuable, followed by standing on 16 vs 10 at TC ≥ 0. The calculator above shows all 18, highlighting active ones based on your current count.

What is the Fab 4?

The four most important surrender deviations: 15v10 (TC ≥ 0), 15v9 (TC ≥ +2), 15vA (TC ≥ +1), and 14v10 (TC ≥ +3). If your casino offers Late Surrender, these are more valuable than learning Illustrious 18 entries #10-18. Toggle “Allowed” in the calculator to see them alongside the I18.

Why should I ever split tens?

At TC +5 or higher against dealer 5-6, the shoe is so rich in 10s that each split ten becomes a strong starting hand while the dealer faces high bust probability. Mathematically correct — but an obvious tell. Most pros skip it entirely to avoid being backed off. The calculator’s “Hide High Heat” option removes these plays.

Do deviations change between S17 and H17?

Some indices shift by ±1 between S17 and H17. The most notable: 11 vs Ace is already a basic strategy double under H17 (no deviation needed), while under S17 it becomes correct at TC ≥ +1. The calculator shows S17-based indices, which work for both rule sets in practice — the 1-point difference rarely affects your decision at the table.

How much do deviations add to my edge?

Play deviations contribute approximately 20-30% of a counter’s total advantage. Bet variation (the True Count driving bet size) provides 70-80%. A counter using only bet variation earns about 60-80% of theoretical win rate. Adding the I18 captures most of the remaining value. Going beyond 18 deviations yields diminishing returns.

What does the index number mean?

The index is the True Count threshold where the deviation becomes mathematically correct. For positive-correlation plays (items 1-13): deviate when TC ≥ index. For negative-correlation plays (items 14-18): deviate when TC < index. The Decision EV Calculator shows the exact EV crossover that makes each deviation profitable.