Card counting
The Illustrious 18: when counters break basic strategy
Don Schlesinger’s short list of the count plays that matter. These 18 deviations capture most of the gain from full index play, so they are where counters start.
What an index is
An index is the true count at which a different play beats basic strategy. “Stand at +4 or higher” means: when the true count is +4 or more, stand; otherwise play basic strategy. “Hit below −2” means: when the true count drops under −2, hit instead of standing.
Indices are rounded and assume multi-deck Hi-Lo. They shift a little with deck count and rules. Learn them after basic strategy is automatic: drill the count here.
Where the list comes from
The Illustrious 18 were published by Don Schlesinger in Blackjack Attack as the answer to a practical question: if you could only memorize a few count-dependent plays, which ones pay the most? He ranked every possible index play by the profit it adds and drew the line at 18. The result covers the large majority of what full index play is worth, in a list short enough to actually learn.
That ranking is why the list looks lopsided. Insurance sits at the top because the decision comes up constantly and the money at stake is large. Splitting 10s against a 5 or 6 at high counts looks dramatic, but it earns its place the same way everything else does: frequency times edge, measured in simulation.
Treat the indices as rounded guides, not physics constants. They assume multi-deck Hi-Lo with standard rules. A few move by a point between dealer-hits-soft-17 and dealer-stands games. The rounded values stay profitable across all of them, which is the point of a short list.
The 18 plays
| Situation | Basic strategy | Count play | At true count |
|---|---|---|---|
| Insurance | Never take it | Take insurance | +3 or higher |
| 16 vs 10 | Hit (surrender if offered) | Stand | 0 or higher |
| 15 vs 10 | Hit | Stand | +4 or higher |
| 10,10 vs 5 | Stand | Split | +5 or higher |
| 10,10 vs 6 | Stand | Split | +4 or higher |
| 10 vs 10 | Hit | Double | +4 or higher |
| 12 vs 3 | Hit | Stand | +2 or higher |
| 12 vs 2 | Hit | Stand | +3 or higher |
| 11 vs ace | Hit (S17) / Double (H17) | Double | +1 or higher |
| 9 vs 2 | Hit | Double | +1 or higher |
| 10 vs ace | Hit | Double | +4 or higher |
| 9 vs 7 | Hit | Double | +3 or higher |
| 16 vs 9 | Hit | Stand | +5 or higher |
| 13 vs 2 | Stand | Hit | Below −1 |
| 12 vs 4 | Stand | Hit | Below 0 |
| 12 vs 5 | Stand | Hit | Below −2 |
| 12 vs 6 | Stand | Hit | Below −1 |
| 13 vs 3 | Stand | Hit | Below −2 |
Insurance is the single most valuable deviation on the list. The 12 vs 4/5/6 and 13 vs 2/3 rows go the other way: with the count deep negative, even standing hands become hits.
How to learn them
After the count is automatic. Deviations are useless, actually harmful, without an accurate true count behind them. If you are still thinking about the count, you are not ready for indices.
Insurance first, then the stiff stands. Memorize the insurance index (+3), then 16 vs 10 (stand at 0) and 15 vs 10 (stand at +4). Those three cover a large share of the list's value.
Learn the negative indices as a group. The 12 vs 4/5/6 and 13 vs 2/3 rows all flip the same way: deep negative count turns stands into hits. One concept, five rows.
Drill them as decisions, not facts. Flash yourself "15 vs 10, true +5" and answer "stand." Rote table-staring does not survive casino pace.
Why only 18
Full index play covers hundreds of situations, but the Illustrious 18 deliver the large majority of the extra edge. Everything past this list is diminishing returns for a lot more memorization.
Frequently asked questions
Do I need to learn all 18 deviations?
Learn them in order of value. Insurance alone is the single most valuable deviation on the list. The 16 vs 10 and 15 vs 10 stands come next. Everything past the first handful is diminishing returns.
Which deviation matters most?
Insurance. Taking insurance at a true count of +3 or higher is worth more than all the other 17 combined for most counters, because it comes up often and the swing is large.
Do the indices change with table rules?
Slightly. The published Illustrious 18 indices assume multi-deck Hi-Lo and are rounded for memorization. A few shift by a point between H17 and S17 games, but the rounded values remain profitable.
Can I use these plays without counting cards?
No. Every deviation is a departure from basic strategy that only becomes correct at a specific true count. Without the count you cannot know when the index applies, and guessing will cost you.
What comes after the Illustrious 18?
Full index play covers hundreds of situations, but the gains shrink fast past this list. Most counters get more from better game selection and bet sizing than from memorizing index number 40.