I recently received this question from a member of our website:

“hey can you explain the importance of deck penetration and if there is any change in strategy for different penetration. Thanks, love the site!”

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Member, thanks for asking, because penetration is incredibly important. First off, I’m going to assume that we’re all mature enough to avoid the jokes pertaining to the obvious sexual innuendo regarding “penetration”. In the world of blackjack, “penetration”, or “deck penetration”, is the amount of cards that the dealer cuts off, relative to the cards dealt out. In the first several months of card counting I gave no attention to deck penetration. I paid attention to the rules and the table minimum. That was it. Then, after reading “Burning the Tables in Las Vegas” by Ian Andersen, I realized that I should try to find games with better penetration. But it was still probably the third or fourth most important factor in my mind.

As I’ve gotten more familiar with the math of the game, and as I have spent more time with simulation software, I’ve realized that deck penetration is drastically undervalued. People think that the main ways to make more money at card counting are to bet more and to play games with better rules.  Did you know that you can add much more value by finding a game with 10% better penetration than by betting 10% more on high counts. Let’s say you’re using a 1-10 bet spread. Now, on a typical game, you’d add around 10-15% to your EV by betting 10% more on all positive true counts. On that same game, if you get 10% better penetration, you’re going to add 40-60% to your EV.

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And that’s not where the benefits end with improved Penetration. The fewer cards that they cut off, the more of a sure thing that game becomes. One of the reasons I don’t play games with poor penetration is because it would take so many hours to overcome variance, it’s not worth the risk.  However, as the penetration gets better, the number of hours necessary to reach the “long run” becomes less and less. I typically won’t touch a six deck shoe game with more than 2 decks cut off.

So next time you head out to a casino, pay careful attention to how many cards they cut off the back of the shoe before dealing out the deck. It often varies from dealer to dealer, so stick to those dealers that offer better penetration. It’ll take fewer hours to guarantee a profit, and your $/hr will skyrocket!

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by Colin Jones