by Norm Wattenberger

Chapter 11. Unusual Effects

This chapter takes some time out to take a quick look at oddities of Blackjack that affect us even though we largely ignore them.

"Are you real or not? It's a fine line." — Warren Zevon, 1994

What is the effect of the cut card?

Some single-deck games and nearly all hand-dealt shoe games deal to a specified point and then shuffle after the current round ends. Some single-deck games deal a fixed number of rounds depending on the number of players. The cut-card effect is the effect on advantage caused by dealing to a fixed point instead of a fixed number of rounds.

This chart compares using a cut card with dealing a fixed number of rounds in a standard single-deck game with one player using Basic Strategy. The red bars show an even 0.2% advantage for the casino for all hand depths when dealing a fixed number of rounds. The green bars show the enormous increase in the casino's advantage in the late rounds when dealing with a cut card. There is a reason for this difference related to card counting even for a Basic Strategy player. In this set of circumstances, if you deal to a cut card you may get five, six or seven rounds depending on the cards. This is because the player and dealer can have hands of two cards or many cards. If there are many high cards (e.g. tens) dealt, we will end up with two- and three-card hands. If there are small cards dealt, we will end up with hands with many cards. So, if we are dealing to a fixed point, and we are dealt a lot of large cards, then we will use fewer cards per round and get an extra round or two. The problem is that these extra rounds will be dealt from a deck with fewer high cards because they have been used up. And we know that a deck with few high cards left is bad for the player.

What is the overall effect?

Now the overall effect is not quite as bad because there aren't as many rounds played at these terrible disadvantages. But there is an effect. This chart shows the difference between a fixed number of rounds and using a cut card. I have included a six-deck game even though six decks is not normally played to a fixed number of rounds. Although it is in most Internet casinos and some Video Blackjack machines. Here we see the overall differences in house edge between cut card and fixed rounds. Note that in single-deck the numbers can change substantially by the exact circumstances, including when the specific dealer chooses to shuffle without a fixed-round rule.

Of course, all that I've shown with all of the above is what was already known. The cut-card adds hands when the deck is lean in tens. So, does this mean that you should avoid single-deck using a cut-card? Probably yes, if you're playing Basic Strategy. But, if you're counting, the effect is minor. Counting cards partially corrects for the effect.

Oddly, it is interesting that all the sources for Basic Strategy house edge ignore this effect even though it exists for the vast majority of games.

Sim details

  • Six decks, S17, DAS, LS, 1 player, Basic Strategy
  • Single-deck, H17, 1 & 4 players, Basic Strategy
  • Six decks ten billion rounds, Single-deck five billion rounds


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