What's the effect of number of decks?

The difference between single-deck and six decks is much more dramatic. Wherever you see a bar pointing up, that hand is responsible for more gain in single-deck than in six decks. The long, downward red bar is player BJ against dealer ace. This hand is less valuable in single-deck because it is less likely that the player will have a Blackjack if the dealer has an ace in single-deck. However, you will see a row of upward bars behind the red, downward bar. This is because player Blackjacks occur more often with single-deck. So, Blackjacks are more valuable in single-deck if the dealer does not have an ace and less valuable if the dealer does have an ace. Overall, BJs are more valuable in single-deck. The longest downward bar is the dark blue bar for TTvsT. A 20 against a dealer ten is a positive-expectation hand. But it occurs less often in single-deck making it substantially less valuable. Single-deck sees a higher win rate in hands 9, 10, and 11 particularly against a dealer 5 because both the frequency and advantage are higher in single-deck. Overall single-deck is better than six decks given the same rules — but as you can see, the effect of specific hands varies greatly.

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 © 2009 Norman Wattenberger