Double-Up Blackjack is a variant of Blackjack in which you can double your bet after you’ve seen your first two cards and the Dealer Up Card, without taking a card. For instance, you have a 20 and the Dealer has a 6 showing, you can increase your bet, up to the amount of the original bet, and stand. In the event of a tie, you lose the Double-Up bet. You can’t Double-Up a Blackjack, although if you split a pair of Aces you can Double-Up any 21 you may be dealt.
The tradeoff is that if the Dealer has, or draws to, a 16 in any combination the hand ends and everyone who hasn’t busted Pushes. You get paid if you have a 21.
This gives us three questions to look at.
Ignoring the Double-Up bet, how do the rule changes affect the results of the Blackjack hands?
On which hands is it advantageous to Double-Up?
Overall, how does this variant compare to regular Blackjack?
I’ve only seen this variant in one casino, and it used six-deck shoes, so that’s what was used here, along with the Six Deck Decision Table. There’s no reason to believe that an eight-deck shoe would be significantly different.
The Blackjack Hands
As expected, the winning percentage of your Blackjack hand was lower in Double-Up than it is on a traditional Blackjack table due to the hands you would have won when the Dealer had a 16. For this analysis, five sets of one million hands each were dealt, for each game, then the median set was chosen from each group. The difference between the two was significant.
Pushes increased by 10.6%, primarily at the expense of wins, which went down by 7.4% while losses were reduced by 3.1%. More significantly the losses were more than ten times higher on the Double-Up game. All bank numbers are in “Units”, with a Unit being whatever you normally wager.
This comparison only looked at the Blackjack hands and would be equivalent to playing at a Double-Up table and never playing the side bet.
The Double-Up Side Bet
Determining the optimum Decision Table for the Double-Up bet was similar to determining the best hands on which to Double Down. 5,000 samples of each initial two card Player Hand (12 – 20) and Up Card (Ace to 10) combination was played, for a total of 450,000 samples. This was done five times and the median set is being used as the example. All five sets came up with the same list of 19 Hand/Up Card combinations which were advantageous to the player.
The Player 18 versus a 5 was within the 95% Confidence Interval of 391, so statistically it’s equal to not placing the Double-Up bet. For more information on Confidence Intervals, see the discussion in Six Deck Blackjack. Some of you may have noticed that the Player 20 or 19 versus a Dealer Ace won more on the Double-Up bet than the hands. This is due to Dealer Blackjacks in which the Dealer’s up card is an Ace but you can’t bet the Double-Up.
Double-Up all 20’s
Double-Up 19’s against a 2 – 8
Double-Up 17’s against a 5 or 7
Regular Blackjack versus Double-Up
In order for this to be a game that you’d want to play, the side bet has to compensate for the lower probability of winning the original Blackjack hand. It’s not even close, which is too bad because it’s a fun game to play. This analysis shows the results of one million hands of each game played. The total hands played adds up to more than one million due to splits.
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