Lesson 15 – The Advanced Course – Part 3

Basic Strategy Variations: Double?

The opportunity to double your bet in return for agreeing to accept only one more card is a very powerful option for the player, if it’s utilized correctly. I can’t tell you how often I see players double hands like 7 or 8 against a dealer’s up card of 6 and then bemoan their fate when they lose. Yes, the dealer is very vulnerable with a 6 showing, but placing an extra bet changes the mathematics of the hand, so all doubles must be well-considered. For example, in a six-deck game where the dealer stands on A-6, doubling a hand of 8 against the dealer’s 6 has a total return of 10.3% whereas just hitting the hand returns 12.3% and the risk is lower!

That said, there comes a time when it is worthwhile to double an 8 against a dealer’s 6 and that’s when there’s a higher proportion than normal of 10s left in the deck. That point is determined, of course, by the true count. As the true count gets more positive, it becomes more profitable to double. Conversely, as the count goes negative, it becomes a better play to hit some hands, rather than double.

Just as you’re using flashcards to learn the hit/stand variations, make up, a set for doubling. Here are the numbers you need:

Basic Strategy Variations Six decks, dealer stands on A-6

Note from the BlackjackInfo.com editor:

There are slight differences in the GameMaster’s index numbers published here and the optimized numbers on the
BlackjackInfo Advanced Blackjack Strategy Cards.

These differences are usually due to the use of risk-averse calculations by the GameMaster. I maintain that for the majority
of players (who are not playing near the maximum Kelly fraction of their bankroll), straight indexes are preferable to
risk-adjusted ones. In any case where risk-averse indexes differ from straight indexes, even by several points,
the decisions are quite close and the effect of choosing one index style over another is minimal.

Soft Doubling

A-2 vs. 4 Double at 3. (Got this? Basic strategy says to HIT A-2 against a 4, but if the true count is 3 or higher, you should double.)
A-2 vs. 5 Double at 0. (Don’t get confused here. Basic strategy says DOUBLE A-2 against a 5, but if the count is at all negative, just hit it; double only when the count is 0 or higher.)
A-2 vs. 6 Double at -1. (or higher. As long as the count remains above -1, you’ll double; once it goes lower than -1, you’ll just hit — then hopefully leave the table if the count doesn’t improve.)
A-3 vs. 4 Double at 1.
A-3 vs. 5 Double at -1.
A-4 vs. 4 Double at 0.
A-7 vs. 2 Double at 1.
A-8 vs. 4 Double at 5.
A-8 vs. 5 Double at 2.
A-8 vs. 6 Double at 1.
A-9 vs. 5 Double at 6.
A-9 vs. 6 Double at 5.

Hard Doubling

8 vs. 5 Double at 6.
8 vs. 6 Double at 3.
9 vs. 2 Double at 2.
9 vs. 3 Double at 0.
9 vs. 7 Double at 6.
10 vs. 9 Double at -2.
11 vs. A Double at 1.


Make up a set of flashcards for these variations and begin working them into your game.

All material in the Blackjack School is © Copyright 2007 The GameMaster Online, Inc.

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37 Comments on "Lesson 15 – The Advanced Course – Part 3"

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Hello to everyone.last night i jump in a bj game that i was already counting with out playing.the numbers was very hot.rc +19 with 3 decks more to be played.on the table me and the dealer only.i make two bets of 20 euro each and the party begins.5 first card guess what !!! Faces and 10.so i have 20 and 20 and the dealer jas 10 and ….. he takes the ace!! Second round … again two boxes/bets of 15 euro and here we go again.i took 2 face cards in the first box second box an ace and an… Read more »
Jan Charles

I don’t really get why you should start doubling on an 11 vs the dealers A when the count is 1. Both you and the dealer basicly have an “11” so the count favours both equally. But you only get 1 extra card while the dealer can keep on hitting. Shouldn’t that give the dealer a little edge over you?

I know its not that important but im just curious why this starts becomming a profitable play. Is it maybe because the dealer busts more often?

Thanks and great work, love this site

Jan Charles

Oh and also, as the count gets bigger the dealer starts getting more Blackjacks which beats a regular “21” right?


I have a crazy question, I play, ” blackjack professional simulator “, by pepperdogsoft.com on my iPhone it is set for six decks, das, h17, surrender and da2 and at rather large true counts it tell me to double hard 12 v a dealer 2 as an I18 suggestion, I have won that a couple of times, but in all my reading I can’t find anywhere else that is suggested, have you ever heard of such a thing.? I thought you should hit 12 v 2 until true 3. Thanks


Are the numbers “running count” or “true count”,,,am a little bit connfused?


Do this Hi-Lo indexes apply with the European blackjack rules??
(no peek, dealer stands at soft 17, double any 2 cards, double after splits, no surrender, 4/6/8 decks)


Most of the deviation play amount to minute practical differences. For the vast majority of players would resources be best spent on focusing on a large enough kitty and supporting the psychology to contain a x10+ spread when normally you would play at best a x8 or x4 spread?


Thanks Ken. I’m just a poor student so I account for every dollar, as such I have a set amount set in stone as my bankroll. Thanks for the comments they are very helpful

I got into an argument with my dad about progressive loss betting systems. His argument was that in a casino where the minimum was extremely low and the maximum was extremely high the casino could be beat. For example, say a casino offered a game with a 10 dollar minimum and a 1,310,720 dollar maximum (I know a casino would never offer this game but just assume they did for the purposes of the example). This would give you a 1-18 spread if you were to double your bet after every loss, not including splits and doubles. My dad argues… Read more »
Thanks for the detailed answer Ken its appreciated. I always thought counters played more aggressively than the kelly due the fact that extremely high counts are rare. It was my understanding then that it is best to get your max bet out at TC 4 or 5. Don Schlesinger for example plays an extremely aggressive spread where his units go up to two as the TC increases slightly. Is this not a normal betting spread for a counter? Do you recommend playing a half Kelly? Or is this all personal preference depending on how high you want your ROR to… Read more »

Why do some of your indices differ from Wong’s when using the same benchmark rules? For example you that the index for a hard 8 v a 6 is a double at TC 3, whereas Wong says it is at TC 1. There are quite a few other examples that differ greatly from yours can you explain why.

Paul Flores

Here in the Mid-South and Gulf Coast – Dealers hit A,6 – they do not stand.

How does this process affect “doubling?”

Michael Revaitis

I am a fairly successful speed count player switching over to the Hi Low system. I see that the Hi Low system is much more powerful system. In many of the variation decisions it is unclear in several cases if the count is true or running. Please advise if possible. Also I am an Atlantic City BJ player with 8 decks. Are the above rules almost the same as 6 decks?

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