What is Deck Penetration in Blackjack? (And Why It’s Important)

When discussing deck penetration in blackjack, we refer to where the cut card is placed to signify it’s time to shuffle. The deeper in the shoe, the better the deck penetration. The better the deck penetration, the easier card counters can gain an advantage over the casino.

If you are not counting cards, deck penetration will mean very little to you or the house’s advantage over you. But for card counters, it’s probably second only behind ensuring that blackjack pays 3 to 2 and not 6 to 5 when deciding on what game to play. 

Blackjack games where more cards can be seen can often overcome the small bumps to house advantage from slightly bad rules. Most players would prefer a double-deck game with a half deck cut off and dealer hit soft 17, rather than dealer stands on all 17s and an entire deck cut off.

Of course, it’s a bit more nuanced than that, but deck penetration is crucial to finding a beatable game, and casinos know this. However, due to a combination of greed and complacency, many Las Vegas casinos still offer good penetration from 1/2 to 2/3 of a deck cut off on a double deck to around just a deck on a six-deck shoe.

Changes for the Better?

The card counting community has mostly accepted the erosion of advantageous house rules over the years; from the slight shrug when Split Aces only got one card to the foretelling of the apocalypse when 6 to 5 blackjack was first introduced, there has been pushback but also a jaded sense of resignation to the golden rule. The one with enough gold to buy the casino gets to make the rules.

But deck penetration is one of those things that hasn’t changed for the worse in the post-Beat the Dealer world. I would argue, though with nothing more than my own recollection, that deck penetration has improved slightly from the late 80s until now.

Recent game reports from both downtown Las Vegas and the Strip show double-deck games where 75% of the cards are being dealt out or where individual dealers may cut less than a deck off of a six-deck shoe; sometimes, even in casinos that have notches in their shoes to show where the cut card should go.

Profit VS Protection

This largesse from the casino is mainly driven by profit motives and not the goodness of their hearts. Casinos make money off the house advantage and the number of hands dealt or slot machines buttons pushed. Shuffling without a machine can take anywhere from a minute to over two on a six-deck table, depending on the dealer and the house shuffle.

With an average of 2.7 cards used in a blackjack hand, times seven spots plus the dealer on a busy Saturday night, we are looking at 22 cards dealt out each round. With five decks or about 260 cards in action, we might see about 12 hands dealt on a full table before it’s time to shuffle. If only four decks are dealt out, we will only see nine, maybe ten.

Many casinos have gone to using shuffle machines that cut down on this wasted time but still getting six decks put in the machine, another six taken out and cut and placed into the shoe is still a lost opportunity, and the public has generally turned their nose up at the continuous shufflers. On top of that, these machines, and more importantly, their maintenance, is costly, especially when multiplied by dozens or even a hundred tables or more.

card shuffler

This is a small disparity of several fewer hands per hour for each table, but again multiplied by every table in a large casino, times 24 hours a day, seven days a week, it’s millions of dollars and the driving factor in why casinos have either left the cut card placement alone or in many cases given even deeper penetration then they did a decade or so ago.

Many consultants and casino managers like Bill Zender have long argued that casinos lose vastly more money to misplaced cut cards and the resulting loss of hands per hour than they would ever lose to card counters, and as surveillance networks and software to spot and remove counters has improved, many casinos have relented and moved the cut card further back in the deck to capture more revenue.

Crucial Cut

Deck penetration is of vital importance because the whole point of counting cards is reaching a point where the balance of remaining high cards to low has allowed us the ability, either through an increased bet or varied play or usually both, where we can gain an advantage over the house.

The number of high cards relative to low, divided by the remaining decks, is the true count. We have to divide by the remaining decks to understand our advantage because if an infinite number of decks were used, we would have no benefit, no matter how high the running count went. We need to understand that the standard deviation of the true count will be much higher as we see more of the cards remaining.

The higher true count in situations where we have very few cards remaining, say maybe 25 or 30 cards remaining at the end of a well-cut double deck with a true count of +4, means we can be much more confident that this imbalance of high cards to low will most likely give us the advantage. But no amount of remaining high cards will help us if they remain behind the cut card.

In situations where more cards are dealt, the true count swings much more wildly. Don Schlesinger in Blackjack Attack indicated that in a game where two decks are cut off a six-deck shoe vs. just one, the number of times the true count will reach +4 almost doubles, and the number of times we can expect to see a true count of +6 nearly triples.

Used To Our Advantage

This means we will have more opportunities to place large bets in shoes with 80% penetration and use Schlesinger’s’ Illustrious 18 or other variations to the basic strategy that can help move the odds in our favor. It also gives us the opportunity to Wong in and out much more profitably due to the number of times the true count reaches +2.

It also means we can more easily weather some minor changes in blackjack rules like dealer hits soft 17. Still, the most essential opportunity it presents is that good penetration can help us play longer.

 In an age of nonstop surveillance and evaluations of blackjack play, it can help us keep spreads down to a more manageable ten-to-one instead of fifteen-to-one or allow us to play more hands at something other than a flat bet. As counts go wildly negative, we can sit out with less concern that we will need to come back in, allowing for more natural cover like telephone or bathroom breaks. And in the right conditions, deeper penetration allows wonging or team play that just isn’t as profitable with less penetration.

Spreads can be kept much tighter in double-deck games, and index use and cover can be significantly enhanced. Spreading of more hands, especially when playing with a partner, may allow even deeper penetration on favorable decks.

Blackjack dealing
Image credit: 888casino

Gift Horse Or Trojan Horse?

For the first time in a very long time, one of the most critical conditions required to count cards successfully turns slightly in the player’s favor. But make no mistake, the casinos are very aware of the increased exposure.

The saying “pigs get fat, hogs get slaughtered” is probably quite apt in this instance. The casinos are more comfortable with deeper deck penetration only because they are more and more successful in spotting and removing counters. A Las Vegas strip property giving you 80 cards out of a double deck is not an invitation to spread $25 to $500 and split 10s the first time the true count hits +5.

Use any newfound advantages in penetration to burrow deeper and hide in plain sight. No amount of increased EV (expected value) will mean anything once you’ve been backed off, and every casino in town has your picture.

Image credit: Dusan Kipic via Unsplash