Double Up Blackjack

Introduction

Double Up Blackjack is a blackjack variant that adds a new option -- the player can double his bet and stand. This option is especially valuable on high totals. However, nothing is ever truly free in the casino. In this case the main price to be paid is that if the dealer draws to 16, he stays, and live bets under 21 push. A player 21 still beats a dealer 16. See the rules section for all the details.

As of this writing, the game can be found in casinos of Colorado, Oklahoma, and the UK.

Rules

It is difficult to find a complete set of rules for this game online. What follows is patched together from various sources. If you believe any of these rules to be in error, please notify me. However, please do not claim that blackjacks pay 3 to 1 per this source, which I firmly claim to be in error.

1. Six decks of ordinary 52-card decks are used.
2. Cards are scored as in conventional blackjack.
3. Conventional blackjack rules, which I assume the reader is familiar with, are followed with the following specifics and exceptions.
4. Surrender is not offered.
5. Re-splitting is allowed, except aces. I do not know how many times.
6. In the UK, the dealer does not take a hole card. However, if the dealer gets a blackjack, the player will only lose his original wager and any other bets he lost due to splitting and then busting. The player will not lose any additional wagers from doubling, splitting (except for busted hands after splitting), or Double Upping.
7. In addition to the usual options with two cards, the player may also Double Up. The player also Double Up on two cards after splitting. The player may not Double Up on a blackjack.
8. To Double Up, the player will make an additional wager, equal to his original wager, in the designated Double Up circle.
9. After splitting aces, the player may only stand or Double Up.
10. After all players have acted, the dealer shall hit to a hard or soft 16. One rule variant is that the dealer may hit a soft 17.
11. If the dealer draws to 16 (hard or soft) he will immediately stand. All live bets on the table, except totals of 21, shall push in this event. In other words, it acts like the Push 22 rule in some games, except applies to a dealer total of 16 instead of 22.
12. Totals of 21 are an exception to the rule above and win against a dealer 16.
13. The Double Up wager shall lose on ties. Please note that this rule applies to the Double Up portion only. The original wager shall still push.
14. Winning player blackjacks pay 3 to 2. All other wins pay 1 to 1.

Strategy

Following are my two basic strategies. They differ by whether or not the dealer hits on soft 17.

The following strategy shows the strategy after splitting aces, when the only options are to stand or Double Up.

House Edge

If the dealer hits a soft 17 I get a house edge of 0.33%. If the dealer stands on soft 17 I get a player edge of 0.10%.

It should be noted that the web site for the game maker, UK Casino Tables Games quotes a house edge of 0.65%. I assume that it is for the hit soft 17 version. The reader will have to decide which figure to believe.

It should also be noted that fellow mathematician Charlie Patrick, who I consider capable and trustworthy, gets a lower edge than I do. He asked that I not publish his specific number.

Methodology

For the sake of simplicity, I assumed an infinite number of decks and infinite re-splitting. I then cut the house edge by 0.1%, which is the effect of six decks compared to infinite in conventional blackjack.

Acknowledgements

I would like to thank Charlie Patrick for his help with understanding the rules of this game and sharing his analysis with me.

External Links

• UK Casino Tables Games — Official page by the game maker.
• Wizard of Vegas — Discussion about the game in my forum.