Play the chart if you are unsure
A missed deviation is a small error. A missed basic-strategy play is a large one. When the true count is fuzzy, take the chart cell.
How to read an index
An index is not a new chart. It is a threshold on the true count. The usual convention: if the true count is at or above the number, take the deviant play. If it is below, take the play on our basic-strategy chart.
Example: 12 versus 3 is a hit on this chart. The common Hi-Lo index is +2, so you stand at true +2 or higher and hit at +1 or below. Negative indexes work the other way on spots the chart already stands: 13 versus 2 stands by default, and you hit only when the true count is worse than -1.
Numbers below are the common published multi-deck Hi-Lo indexes for a dealer who stands on 17. They can move by a point depending on the book and the exact number of decks. Our four-deck game is in that family. They are not a license to ignore surrender, 6 to 5, or a dealer who hits soft 17.
Common Hi-Lo indexes
Each row starts from our chart, not from a generic no-surrender grid. That is why 16 vs 10 is listed as surrender first. True count is the Hi-Lo true count from the counting guide, rounded the same way as the trainer: to the nearest half.
Insurance
The single most valuable play change. It does not touch the main chart.
- Dealer ace showingTC +3
Chart: Never take insurance
Take insurance (and even money)
| Spot | Chart | Index | Instead |
|---|---|---|---|
| Dealer ace showing | Never take insurance | +3 | Take insurance (and even money) |
Hit or stand, no surrender
Use these when the table does not offer surrender. Our chart already surrenders 16 vs 9, 10, and ace, and 15 vs 10. Keep surrendering those; standing is not an upgrade.
- 16 vs 10TC 0
Chart: Surrender, else hit
Stand if you cannot surrender
- 15 vs 10TC +4
Chart: Surrender, else hit
Stand if you cannot surrender
- 16 vs 9TC +5
Chart: Surrender, else hit
Stand if you cannot surrender
- 12 vs 3TC +2
Chart: Hit
Stand
- 12 vs 2TC +3
Chart: Hit
Stand
| Spot | Chart | Index | Instead |
|---|---|---|---|
| 16 vs 10 | Surrender, else hit | 0 | Stand if you cannot surrender |
| 15 vs 10 | Surrender, else hit | +4 | Stand if you cannot surrender |
| 16 vs 9 | Surrender, else hit | +5 | Stand if you cannot surrender |
| 12 vs 3 | Hit | +2 | Stand |
| 12 vs 2 | Hit | +3 | Stand |
Extra surrenders
Late surrender only. Our chart already covers 15 vs 10 and 16 vs 9-A. These add three more spots.
- 15 vs 9TC +2
Chart: Hit
Surrender
- 15 vs ATC +1
Chart: Hit
Surrender
- 14 vs 10TC +3
Chart: Hit
Surrender
| Spot | Chart | Index | Instead |
|---|---|---|---|
| 15 vs 9 | Hit | +2 | Surrender |
| 15 vs A | Hit | +1 | Surrender |
| 14 vs 10 | Hit | +3 | Surrender |
Doubles
If you cannot double, take the chart fallback: hit.
- 11 vs ATC +1
Chart: Hit
Double
- 10 vs 10TC +4
Chart: Hit
Double
- 10 vs ATC +4
Chart: Hit
Double
- 9 vs 2TC +1
Chart: Hit
Double
- 9 vs 7TC +3
Chart: Hit
Double
| Spot | Chart | Index | Instead |
|---|---|---|---|
| 11 vs A | Hit | +1 | Double |
| 10 vs 10 | Hit | +4 | Double |
| 10 vs A | Hit | +4 | Double |
| 9 vs 2 | Hit | +1 | Double |
| 9 vs 7 | Hit | +3 | Double |
Pair of tens
High variance. The chart stands on 20 for a reason. Learn these last.
- 10s vs 5TC +5
Chart: Stand
Split
- 10s vs 6TC +4
Chart: Stand
Split
| Spot | Chart | Index | Instead |
|---|---|---|---|
| 10s vs 5 | Stand | +5 | Split |
| 10s vs 6 | Stand | +4 | Split |
Leave the stiff at a minus count
The chart already stands these. At a very negative true count the remaining tens are scarce, so hitting becomes better.
- 13 vs 2TC -1
Chart: Stand
Hit below -1
- 13 vs 3TC -2
Chart: Stand
Hit below -2
- 12 vs 4TC 0
Chart: Stand
Hit below 0
- 12 vs 5TC -2
Chart: Stand
Hit below -2
- 12 vs 6TC -1
Chart: Stand
Hit below -1
| Spot | Chart | Index | Instead |
|---|---|---|---|
| 13 vs 2 | Stand | -1 | Hit below -1 |
| 13 vs 3 | Stand | -2 | Hit below -2 |
| 12 vs 4 | Stand | 0 | Hit below 0 |
| 12 vs 5 | Stand | -2 | Hit below -2 |
| 12 vs 6 | Stand | -1 | Hit below -1 |
Index drill
16 vs 10 at true count -2
Chart play: Surrender, else hit. Deviation at TC +0: Stand if you cannot surrender.
What is worth memorizing first
You do not need every index on day one. Most of the extra edge is in a short list.
- Insurance at +3
- Take it, including even money on your own blackjack. Below +3 it is still a no. This one play is worth more than most of the grid changes combined.
- Stiffs versus 10, no surrender
- If the table will not let you surrender, stand 16 vs 10 at true 0 or higher instead of hitting, and stand 15 vs 10 at +4. If surrender is offered, our chart already takes it. Do not stand just because you saw the famous index.
- Leave the rest until the count is boring
- Extra surrenders, 11 vs ace, and splitting 10s add less and cost more concentration. Splitting 20 is high variance. Learn it last.
How this fits the rest of the site
Deviations are the last layer, not a parallel track.
- Chart first
- Every index assumes the S17, multi-deck, 3 to 2 chart. If a cell is not automatic at a true count of zero, you will fire the deviation on the wrong hands.
- True count second
- Running count is not the index. Divide by decks remaining. The counting trainer grades that conversion. Use it until the true count is as automatic as a hard 12.
- Index drill
- The quiz below asks chart or deviation at a true count. The counting trainer still grades the count itself. Do the count first.
How to use a deviation in a round
The count comes first. The index is a lookup after you already know the true count and the chart play.
Get the true count
Running count divided by decks remaining, nearest half. Insurance and these cells use that number, not the raw running count.
See if this hand is an index spot
Most hands are not. 16 vs 10, insurance, 12 vs 2 or 3, and 11 vs ace come up enough to be worth the effort. Pair of tens vs 5 does not.
Compare to the number
At or above the index, take the instead-play. Below it, take the chart, including surrender and double fallbacks.
What deviations are for
- Flipping the close cells once the remaining shoe is no longer average.
- Taking insurance when the ten-density finally pays.
- Standing a no-surrender 16 vs 10 at a non-negative true count.
- Adding a few extra surrenders and doubles on top of the chart.
What deviations are not
- A replacement for the chart. At a true count near zero, the chart is still correct.
- A substitute for betting with the count. Most of the counting edge is in the bet size.
- A reason to skip surrender on 16 vs 10 when the table offers it.
- A full Illustrious 18 dump you have to recite before you can count. Start with insurance.
Chart play versus the index
Same four-deck, stand-on-17, 3 to 2 game. The left column is what our chart already does. The right column is the Hi-Lo change.
Insurance
Our chart (true count near 0)Never. The 2 to 1 payout is not enough.
Common Hi-Lo deviationTake it at true +3 or higher, including even money.
16 vs 10
Our chart (true count near 0)Surrender if the table allows it, otherwise hit.
Common Hi-Lo deviationIf there is no surrender, stand at true 0 or higher. If there is surrender, keep surrendering.
12 vs 3
Our chart (true count near 0)Hit. The dealer 3 is not weak enough to stand a 12.
Common Hi-Lo deviationStand at true +2 or higher.
11 vs A
Our chart (true count near 0)Hit. On this S17 chart you do not double 11 into an ace.
Common Hi-Lo deviationDouble at true +1 or higher. If you cannot double, hit.
Blackjack deviations FAQ
What is a blackjack deviation?
A play that differs from basic strategy because the true count says the remaining shoe is richer or poorer in tens and aces. The threshold is the index. Below it, use the chart.
Do I stand 16 vs 10 at a true count of 0?
Only if surrender is not offered. Our chart already surrenders 16 vs 10, 16 vs 9, 16 vs ace, and 15 vs 10. Surrender beats standing there. The famous stand-at-0 index is the no-surrender version of that hand.
Which deviation should I learn first?
Insurance at true +3. Then the no-surrender 16 vs 10 stand, then 12 vs 2 and 12 vs 3, then 11 vs ace. Pair of tens can wait.
Are these the Illustrious 18?
They are the same family of multi-deck Hi-Lo indexes, written against our S17 chart instead of a generic no-surrender grid. That is why insurance and 16 vs 10 are explained with surrender in mind. Published numbers can differ by a point.
Does the strategy trainer grade deviations?
No. The strategy trainer grades the chart at a true count of zero. The counting trainer grades running and true count. The quiz on this page asks chart or deviation at a true count.
What if I am between indexes, like true +1.5?
The trainer rounds true count to the nearest half. If the index is +2, +1.5 is still below it. Take the chart. Do not invent a maybe.
Can I skip deviations and still count?
Yes. Most of a counting edge is betting more at a high true count and less at a low one. Deviations are a thinner layer. They are worth learning after the count is automatic, not before.
Get the true count first
These cells only help if the true count is right. The counting trainer deals the same four-deck, stand-on-17, 3 to 2 game, then asks for running and true count. After that, use the quiz on this page.