Blackjack Deviations Guide (When to Deviate from Basic Strategy)

Q: Do I need deviations if I am not counting?

No. Deviations only make sense if you know the true count. Without the count, basic strategy is the correct play.

Q: How many deviations matter most?

The Illustrious 18 capture the majority of EV from deviations. Start there before learning long lists.

Q: Do deviations change with rules?

Yes. Rule sets like H17 vs S17 shift some indices. The largest deviations stay similar, but exact numbers can move by 1.

What Is a Deviation?

A deviation is a deliberate break from basic strategy when the true count says the deck is unusually rich in high cards or low cards. Basic strategy assumes a neutral shoe. Deviations exploit the temporary bias of the remaining cards.

The most valuable deviations typically involve standing more often, doubling more aggressively, and taking insurance at high counts.

Why Deviations Work

When the true count is high, tens and aces are more likely. That increases blackjacks, dealer busts, and the EV of doubles. When the count is low, the opposite happens and you play more conservatively.

The highest EV deviations also happen on the most common hands, which is why the Illustrious 18 capture so much value with only a small memory load.

High-Value Deviations to Learn First

This list assumes a 6-deck shoe, S17, DAS. Treat the counts below as "or higher" unless marked as "or lower."

Hand	Dealer	Basic Strategy	Deviation	True Count
16	10	Hit	Stand	TC 0+
15	10	Hit	Stand	TC +4+
10	10	Hit	Double	TC +4+
12	3	Hit	Stand	TC +2+
12	2	Hit	Stand	TC +3+
11	A	Hit	Double	TC +1+
9	2	Hit	Double	TC +1+
9	7	Hit	Double	TC +3+
13	2	Stand	Hit	TC -1 or lower

Memorize the play, not just the number. You should be able to answer "16 vs 10" instantly before checking the count threshold.

How to Use True Count Thresholds

Think of each index as a switch. If the true count meets or exceeds the index, you deviate. If it does not, you follow basic strategy.

Example: 10 vs 10, index +4. At TC +4 or higher, double. Below +4, hit.
Example: 13 vs 2, index -1. At TC -1 or lower, hit. Above -1, stand.

Practice Plan That Sticks

Learn the top 5 deviations and drill them for 200 hands.
Add the next 5 and drill for another 200 hands.
Only then move to the full Illustrious 18 list.

The Blackjack 3000 drills will surface your most missed deviations so you focus on the high-impact mistakes first.

Heat Management for Deviations

Large deviations can look suspicious if you slam the opposite play every time. To reduce heat:

Use consistent, simple language if asked ("I feel like standing").
Avoid dramatic bet jumps and deviations on the same hand.
Pick tables with more players so your patterns are harder to spot.

Common Mistakes

Deviating without a true count. Running count alone is not accurate across shoe depth.
Mixing rule sets. H17 and S17 indices are different. Stay consistent.
Overvaluing rare deviations. Focus on common hands first.

Frequently Asked Questions

Do I need deviations if I am not counting?

No. Deviations only work when you know the true count. If you do not count, stick to basic strategy.

How many deviations matter most?

The Illustrious 18 capture the majority of deviation EV. Learn those before deeper lists.

Blackjack Deviations Guide