The Illustrious 18, and when to break the chart

What is the Illustrious 18?

The Illustrious 18 is the list of the eighteen most valuable Hi-Lo index plays: the spots where a card counter should depart from basic strategy. Basic strategy tells you the best play for every hand, assuming you know nothing about which cards are left in the shoe. A card counter does know something, and when the remaining cards are rich in tens and aces, a few plays that are normally wrong become right. Each of these switch points is called an index play.

There are hundreds of possible index plays. Don Schlesinger, in his book Blackjack Attack, ranked them by how much each one is worth and found that a short list of eighteen captured most of the gain. That list became known as the Illustrious 18. The point is practical: learning eighteen numbers gets you most of the benefit of learning two hundred.

How do blackjack index numbers work?

Each index is a true count at which you change your play. At that count or higher, you make the deviation. Below it, you follow basic strategy. Take 16 against a dealer 10 with an index of 0. Basic strategy says hit. But once the true count is 0 or higher, you stand, because there are enough tens left that hitting busts you too often.

The true count matters here, not the running count. You divide the running count by the number of decks left in the shoe, so a running count of +6 with three decks remaining is a true count of +2. If that's still hazy, the card counting drill walks through it hand by hand, and the chart above assumes you've already got that part down.

The plays that matter most

The list is ranked, and the top of it does most of the work. Insurance comes first: basic strategy says never take it, but at a true count of +3 or higher, more than a third of the remaining cards are tens and insurance becomes a profitable bet. The insurance calculator shows why the maths flips.

Next come 16 against a 10, where you stand at 0 or above, and 15 against a 10, where you stand at +4. These hands come up constantly, which is why they're worth so much. The 16 against 10 decision is closer than most people think: when we simulated it two million times each way off the top of the shoe, hitting cost 57.1p per £1 and standing 57.5p. A fraction of a penny separates them, so it takes only a neutral count to tip the balance toward standing. After that, the splits of tens against a 5 or 6 at high counts, and the doubles on 10 and 11, add value but come up less often. The negative indices at the bottom of the list, like standing on 12 against a 5 even at -2, are really about when to hit a stiff hand you'd normally stand on.

H17 indices

A few indices shift. When the dealer hits soft 17, doubling 11 against an ace becomes right at a lower count, -1 instead of +1, and doubling 10 against an ace comes in at +3 instead of +4. Standing on 12 against a 6 holds down to -3 rather than -1, and surrendering 15 against an ace starts at -1 rather than +1. The toggle above switches the chart and the drill between the two rules, so practise the one you'll play. The basic strategy chart has the same toggle for the underlying plays.

What are the Fab 4 surrender plays?

They're the surrender version of the same idea, published alongside the Illustrious 18 for games that offer late surrender. Surrender 14 against a 10 at +3, 15 against a 10 at 0, 15 against a 9 at +2, and 15 against an ace at +1, or -1 if the dealer hits soft 17. Because surrender saves half your bet on a hand you're likely to lose, getting these right at high counts is worth a surprising amount. If the table doesn't offer surrender, skip them. The surrender advisor covers when it's available.

Is using the Illustrious 18 legal in the UK?

Counting cards in your head is legal. There's no law against keeping track of the cards and changing your play, and that's all the Illustrious 18 is. What isn't legal is using a device, app or smart glasses to count for you, which breaches casino terms and can fall under UK cheating law.

The catch is that a casino can refuse your play or ask you to leave if it suspects counting, and live dealer studios watch for betting patterns that track the count. Online RNG blackjack shuffles a fresh deck for every hand, which makes counting, and every index play, pointless. The live dealer AI page explains how studios monitor play.

Order of learning

Learn them in ranked order, and only once basic strategy is automatic. Bear in mind the count reaches +3 on fewer than one round in eleven in a six-deck shoe, so the top few plays are the ones you'll use most.

• Get basic strategy perfect first with the strategy chart. Deviations add little if the basics slip.
• Practise the true count conversion with the Hi-Lo drill until it takes a second.
• Drill the top five plays above until you get them right every time, then add the rest a few at a time.