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# Deal Me In: Times to split 10s at blackjack are extremely rare

27 February 2015

Dear Mark: I am aware that you never – ever – ever split 10s against a dealer’s 5 or 6. However, I have been tempted to do so when no one else is at the Blackjack table. My question is what is the percentage odds of winning (or losing) by doing so? Herb C.

Surprisingly, Herb, there was a gaming writer, John Scarne (Scarne on Cards), who did recommend splitting 10s when playing the standard version of blackjack. However, Scarne’s book was published in 1949, well before computers could analyze the game of blackjack with multimillion-hand simulations.

Then in 1962 along came Edward Thorp, the first blackjack specialist, who used an IBM 704 computer and published the results in his book, "Beat the Dealer." Since then, I can’t think of any blackjack authors who recommend splitting 10s in most, if not all, cases.

Moreover, years ago I ran a 20-million-hand simulation analysis using a Macintosh software program called BJ Trainer. My results clearly favored leaving those 10s unaided versus splitting them, even against a 5 or a 6. I favor taking computer results over advice written in 1949 every time.

That said, Herb, in reference to your question where you state “Never – ever – ever split 10s against a dealer’s 5 or 6” there are moments where it could be a good strategy.

In Face-Up Blackjack, where all the cards dealt are exposed, including both dealer’s cards, the correct strategy calls for splitting 10s against the dealer’s 13, 14, 15 or 16.

Also, for card counters, a situation that favors splitting 10s would be when there is a high proportion of high cards left in the deck, for instance, a high-low true count of plus 6 or more with the dealer showing a 6.

There is one other scenario where splitting 10s can be a better play than standing, that being the last hand of a round during a blackjack tournament. I had it happen to me once when, while observing the leader’s chip count, I calculated that by holding on to a probable winner of 20, I still wouldn’t have won enough money to overtake him. So, Herb, I split them, and a \$20 payout difference got me to the next round.

As for the arithmetic, the statistical data on how often you will win when you split a pair of 10s against a dealer showing a 6 is 64 percent of the time. Your profit expectations for every \$100 you bet while splitting those 10s will be, on average, a \$56 profit.

However, Herb, we had better look at your other option: standing pat on your 20. By standing, you will win around 85 percent of the time, and will make about \$14 more per \$100 wagered than splitting.

My recommendation is to stand on your 20. Your fair share of being dealt a 20 is approximately 9.2 percent of the time, and I just don’t want you putting that stellar hand in unwarranted jeopardy, but for those few exceptions listed above.

Gambling Wisdom of the Week: "Blackjack - what a game! How simple it looks, yet how complex it truly is.” – Victor H. Royer
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Mark Pilarski

As a recognized authority on casino gambling, Mark Pilarski survived 18 years in the casino trenches, working for seven different casinos. Mark now writes a nationally syndicated gambling column, is a university lecturer, author, reviewer and contributing editor for numerous gaming periodicals, and is the creator of the best-selling, award-winning audiocassette series on casino gambling, Hooked on Winning.
Mark Pilarski
As a recognized authority on casino gambling, Mark Pilarski survived 18 years in the casino trenches, working for seven different casinos. Mark now writes a nationally syndicated gambling column, is a university lecturer, author, reviewer and contributing editor for numerous gaming periodicals, and is the creator of the best-selling, award-winning audiocassette series on casino gambling, Hooked on Winning.