The GameMaster's Blackjack School

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

To start at the beginning, visit the Welcome page.

Lesson 15 - The Advanced Course - Part 3

by the GameMaster, reprinted with permission.
The Blackjack School is also available on DVD from the GameMaster's Store.

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 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. 4Double 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. 5Double 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. 6Double 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. 4Double at 1.
A-3 vs. 5Double at -1.
A-4 vs. 4Double at 0.
A-7 vs. 2Double at 1.
A-8 vs. 4Double at 5.
A-8 vs. 5Double at 2.
A-8 vs. 6Double at 1.
A-9 vs. 5Double at 6.
A-9 vs. 6Double at 5.

Hard Doubling

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


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

Questions? E-mail me at and I'll reply personally.

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