Blackjack Card Counting — Introductcion

Last update: Apr. 2, 2008

Why does card counting work? There are various reasons. Here are some of the major ones, in no particular order.

1. The dealer must hit a stiff hand (total of 12 to 16), while the player does not. Correct basic strategy is to stand with a stiff hand against a dealer low card (2 to 6), except a 12 against a 2 or 3, which the odds favor hitting. The player can also get out of some stiff hands by splitting. In a one on one game, the player will bust about 13.0% of hands, and the dealer 28.2%¹. If the remaining cards are rich in big cards, that will increase the probability of busting a stiff hand. This increased probability of busting works against both player and dealer, but the dealer more, because he is forced to hit stiff hands.
2. There will be more blackjacks when the deck is rich in tens and aces. While the dealer will get just as many blackjacks as the player, the 3 to 2 payoff makes blackjacks more valuable to the player overall. Blackjacks will also tend to occur when counter bets big, because he knows when the remaining cards are ten and ace rich.
3. Player doubles are more successful in decks rich in tens and aces, when the counter will be betting more.
4. Player splits are more successful in decks rich in tens and aces, because they are disproportionately against weak dealer cards. In high counts, when the counter bets more, the dealer will bust more often when the player splits.
5. Insurance is a valuable play to the counter. If the remaining cards are rich in tens, insurance becomes a good bet.

For these reasons, tens and aces are good for the player, and small cards are good for the dealer². What the card counter does is keep track of the cards as they come out, which tells him what to expect of the remaining cards. If he knows the future holds a disproportionate number of tens and aces, he bets more. Likewise, if he knows the future holds lots of small cards, he bets less, or better yet, nothing. The counter will also deviate from basic strategy sometimes, according to how rich the remaining shoe is in small or big cards.

While card counting is a reliable and legal way to beat the casinos, television and movies consistently portray card counting to be an easy road to huge riches. If it were, everyone would be doing it. The fact of the matter is that card counting is hard work for a small advantage. The casino floor supervisors know the basics of card counting, and have access to software to gauge your skill level, by following what you do from the surveillance room. There is always a tradeoff between short-term profits and long-term access to play. If a casino supervisor suspects you of counting, he will usually have no compunction to prohibit you from playing.

About the best you can expect as a card counter is a 1% advantage. The exact advantage will depend on how strong a strategy you use, game rules, the ratio of your high bet to low bet, how deeply into the shoe the dealer places the cut card, and your skill level as a counter, among other factors.

There is an almost endless amount that has been written on card counting. I will attempt only to scrape the surface, and offer some other good resources for further reading. The following list shows where you can go from here.

Footnotes

1. Both player and dealer probability of busting include frozen hands, where either party has a blackjack. The dealer probability of busting reflects hands frozen because the player busted. If the player splits, the bust percentage includes all subsequent hands. My player probability does not agree with that of Don Sclesinger in Blackjack Attack (page 50, 2004 ed.) I believe the reason for the difference is we measure the statistic differently.
2. Blackjack appendix 7

Further Reading

Hi-Lo Count: The gold standard of blackjack card counting strategies.
Wizard Ace-Five Count: Very easy and simple card counting strategy.
Blackjack appendix 7: Value of each card to the player.
"21" Movie Review: Truth and fiction about the movie about the MIT card counting team.
Blackjack book reviews.
Main blackjack page.