Lesson 23 – Beating the Double-Deck Game – Part 3

This free course on blackjack and card counting was created by the GameMaster, publisher of the GameMaster Online website. It is reproduced here in its entirety with permission of the author. His 24-lesson course is an excellent introduction to winning blackjack.

To start at the beginning, visit the Welcome page.

Double Deck Basic Strategy Variations

Beating the double-deck Blackjack game requires that you first find a game that offers decent penetration and a minimum bet that will allow you to spread your bets from 1 to 8, yet still stay within reasonable money management principles based upon your total bankroll. Another “arrow in your quiver”, so to speak is to vary the play of your hand according to the count.

If you know how to count cards, you can use the count to tell you how much to bet on each hand, but you can use the count to help you play each hand more accurately, too. If you’ve studied my course up to this point, you know one of the key factors in playing a winning game of Blackjack is to leave the table when the True Count drops to -1 or lower, but that tactic isn’t very practical at most double-deck games because fewer rounds of hands are dealt before the shuffle, as compared to a six-deck game.

Consequently, you have to sit through a lot more “negative” decks, but the good thing is that a shuffle is never too far away. Yet, at the same time, we all know the casino’s edge increases as the count drops, so we want to neutralize the effects of that as much as possible. Because you’ll likely be sitting through many more negative counts at a double-deck game, what we need to do is learn the plays for hands like hitting 12 against a dealer’s 5 and so forth. We also want to avoid doubling and splitting pairs in low counts and we’ll hit instead. But we don’t want to guess at important plays like that, so we’ll need to learn Basic Strategy variations for “lower” numbers, like -2, -3 and so forth. A realistic range for most double-deck games is a True Count of -6 to +6 and that will cover 85% of all the hands you’ll ever play, assuming 50-60% penetration.

Some players prefer to learn just the indices for the most common hands, with the idea that they’ll get a hand like A, 4 against a 5 less than 100 times in every 100,000 hands of play, but they’ll have a 16 against 10 much more often. In his book, “Blackjack Attack“, Don Schlesinger devoted a chapter to what he calls “The Illustrious 18” that are, in his opinion, the most important Basic Strategy variations. I’m not big on reproducing other authors’ original works, so I’ll refer you to the book for a complete listing if you feel you’d rather not memorize all of the variations I’ve listed here. Another idea worth considering is to not learn the indices below -2, with the rationale that you’ll likely be betting the minimum in such a count, so any playing mistakes will, in the long run, cost you very little. Or, you might want to learn only the indices where you’ll be placing extra bets on the table, as in doubles and splits, with the idea that, if I’m going to be putting more $$$ on the table, I’m sure as hell going to play the hand correctly.

But I’m of the opinion that if something about this game can be learned, it should be learned. (Okay, I know I’m a fanatic for this stuff, but what can I do?) If double-deck games will be where you’ll spend most of your time, then it’s probably worth the effort to memorize all the indices presented here. But if this isn’t your primary game, a range of -2 to +6 with some judicious editing will probably suffice. Don’t forget that most of these indices are similar to those for a six-deck game, so you won’t be starting from scratch. Learn those numbers you think are important for where and how you play.

Rather than talk you through each hand’s variation, as I did in the multi-deck section, what I’ve done here is produce a Basic Strategy Matrix that shows an “index” number for each appropriate play. Don’t worry if you have a problem understanding it, because I’ll explain it all at the bottom.

Basic Strategy Variations Matrix
Double Deck, H17, Da2, no das, no surrender
See the matrix. (Use your back button to get back here.)

Using the Matrix

(GM Note: The Basic Strategy for this game is available from BlackjackInfo.com: 2D, H17, DA2, NDAS Basic Strategy)

It’s a lot easier to use this matrix if you’ve memorized the Basic Strategy for this game and if you haven’t yet done that, you really should learn it before you get into this advanced mode of play. For each player hand and dealer’s up card combination you will see either a specific action, such as hit, stand, double, etc., or a number. The number is an “action point” based upon the True Count and it keys the variation. As to what the proper variation is for a situation may get a little confusing, but if you study the hand in question, you can usually figure it out. A good example of this is A,7 versus a dealer’s 2. In the matrix, you’ll see the number 2 in that spot, so do you hit or stand or do something else? Well, “something else” is the answer, so you should double, just as you do with A,7 vs. 3, 4, 5, and 6. Logic plays a role here, so if a play sounds illogical, it’s probably the wrong one. Would you really hit A,7 against a 2? Of course, you might stand, but that’s already the Basic Strategy play, so doubling is all that’s left. Consequently, what this is telling you is that you should double A,7 against a dealer’s up card of 2 when the True Count is 2 or more. If the True Count is less than 2, use the Basic Strategy play, which is to stand. Against a 3, Basic Strategy says to double A,7. But the index for that is -2, so that’s telling you to double A,7 vs. 3 only if the True Count is -2 or higher. If it’s not, then you should stand. Let’s talk about another variation that may cause some confusion: 8, 8 vs. 10. The notation in that box is “Stand@6”, so if the True Count is 6 or more, you will not split the 8s, but stand instead.

The general rule for understanding the Basic Strategy Variations Matrix is this: If the number in a slot is 0 or a minus, then that play is a Basic Strategy move that you should make as long as the count is higher than the number shown. For example, with A,4 vs. 4, you will double as long as the count is 0 or higher. If the count is minus, just hit. In the case of 9 vs. 4, you’ll double as long as the count is -3 or higher (remember that -1 is “higher” than -2).

I don’t want you to leave without me telling you the most important variation of all, which is the Insurance bet. You hopefully know that proper Basic Strategy tells us to never take insurance (even when you have a ‘natural’ and the dealer’s up card is an Ace, in spite of what everybody else tells you), but in a double-deck game, the insurance bet becomes profitable at a True Count of 2 (actually 2.4 if you can achieve that degree of accuracy) or higher.

Learning the Basic Strategy Variations

Once you’ve chosen the Basic Strategy variations you want to learn, you should make a set of flash cards for them. Exactly how to do that is explained in Lesson 14 of “The GameMaster’s Blackjack School” and I cannot over-emphasize their value. Make up a set and carry them with you, or at least study them intently before each playing session if double-deck Blackjack isn’t your “primary” game.

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13 comments on “Lesson 23 – Beating the Double-Deck Game – Part 3

    • I have no idea why there was no data for the pair of 10s in GameMaster’s chart. I’m guessing it was accidentally removed during editing at some point.

      I have added in the missing line on the matrix page. All set now.
      (Split TTv5 @ +5. Split TTv6@ +4.)

      Thanks for catching that!

  • Donald said:

    Thanks, Ken, for the very detailed response. Your last point is especially helpful in explaining the larger discrepancies which were particularly concerning/confusing to me.

    So for 9 vs 2 >> – 1, 2 which has a large difference and crosses the +/- threshold, the edge changes slower and the basic strategy decision to ‘double’ (index -1) is close enough that after factoring in risk-aversion it would change the BS decision to ‘hit’ (as the index is >=2)?

    On a side note, though I know the incremental expected value is small, are you able to provide or can I purchase your full index sets beyond -5 to 5 for the six sets of rules if you have them?

    • During the iterative process of generating the indexes, I truncated the list to only -5 to +5 at each step of the process, so I do not have the outlying indexes. Wong’s Professional Blackjack has a wider range for shoe games in H17 and S17 if I recall correctly.

      • Donald replied:

        ok thanks, I’ve gone back to Professional Blackjack and found the wider index ranges for H17 & S17 shoe games.

        One last question (at least for now!) on Double Deck. On your Adv Charts the index value for A,3 vs 4 = 1 for both H17 & S17. However the basic strategy action is Hit (S17) and Dbl (H17). I know this scenario is a close one but what’s the reason for the differences in basic strategy between H17 & S17 despite the same index.


        • It’s just a close call, and the optimal basic strategy happens to change between S17 and H17. Yet the index numbers round to the same value. Just another of the subtleties that emerge from the game.

  • Donald said:

    Hi Ken,

    I have your Advanced Card Set (which are very helpful and I would highly recommend to everyone). I am building a custom playing strategy in CVBJ for DD as I’ve been wanting to learn correct BS and Indices instead of the composite. Comparing the indices on your 2D, H17 card to the matrix you’ve linked above, I’m seeing several differences, are there certain rule assumptions in the two sets of indices that I’m overlooking?

    Just looking at the top of hard total section for example (>> card index, link index)
    8 vs 5 >> 3, 6
    8 vs 6 >> 2, 3
    9 vs 2 >> -1, 2
    9 vs 3 >> 1, 0
    9 vs 4 >> -3, -3 (same)
    9 vs 5 >> -5, -4
    10 vs 9 >> -2, -1


    • I have struggled with how to deal with the discrepancies between the GameMaster’s published index numbers and the ones I spent so many hours devising for the strategy cards. GM himself noted that he used risk-adverse index numbers, and that explains most of the differences, although not all. My choice to not risk-adjust my indexes is based on the fact that exceptionally few players bet near a Kelly fraction of their true bankroll. Even players who do make bet sizing calculations based on Kelly tend to use the amount of money they have on hand for gambling right now, with no consideration of future income streams. Of course, that does reduce risk of ruin, and I am definitely not saying that is a bad idea. But it does taint any risk-averse calculations that are based on the lower bankroll estimates. If you choose to use risk-averse numbers, then the appropriate index number literally depends on the size of your bet on that specific hand at the time, which seems ridiculous to have to consider. And it is not like risk-averse indexes can magically make the game far less risky. They have a very small effect, despite the considerable complexities they cause. I prefer (and use) straight index numbers, and comfortably know that I’m doing the right thing because I am not risking anywhere near a Kelly fraction of my bankroll anyway. (In that case, risk-averse and non-adjusted indexes are identical anyway!)

      I mention the differences between his indexes and mine inside the lesson at https://www.blackjackinfo.com/blackjack-school/lesson-14-advanced-course-part-2/ .
      But the discrepancies do make me uncomfortable, and they require a lot of explanation to readers. Witness this lengthy reply! Since I cannot get in touch with GameMaster to discuss a resolution, I have left things as they are so far. But, as time passes, I become more convinced that I should simply edit all of his index numbers so that they are consistent with mine. I spent hundreds of hours optimizing my numbers, and have a great deal of confidence in their utility. Generating index numbers is much more involved than most people realize. Each number is also dependent on the choice of index numbers further down the decision chain. That is, determining an accurate index for 14vT also depends on the values chosen for 15vT and 16vT, since those are among the possible outcomes for hitting 15vT. It is a lengthy recursive process. I don’t know what method GameMaster used to generate his numbers, but I doubt that his methodology was as careful as mine. For that reason, I completely recommend my values. If there is a difference, I say use my number.

      The good news is that when the index differs by more than a point or two, that indicates a situation where the edge likely changes slowly as the count changes. That means the most contested numbers are likely those that matter the least, where a point or three won’t affect your results much at all. The truth is that if you were to use all of his numbers vs all of my numbers, the difference in expected results is small.

  • Carl McKay said:

    Hey Ken, many thanks for all you do. Could you point me to where I can find a basic strategy variations matrix for all of the same parameters you listed on this page except that the dealer stands on a soft 17?(Double Deck, H17, Da2, no das, no surrender)

  • James M. Paquin said:

    Today’s date is 12-30- 2015. I’ve always asked myself, ” Is there more than just basic strategy ? ”
    Double deck is my game, the only one I can find without continuous shufflers. Thankyou for this info.

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