Posted by: phedrick | September 30, 2008

Blackjack and Counting Cards

I’m a pretty avid poker player, but one game I generally don’t play is blackjack (I usually stick with Texas Hold’Em). The only reason I don’t play is because I’ve never really sat down and learned the strategy behind it. With Casino Night coming up at the end of the semester, though, I figured it’s time to brush up on card skills so we can rack up those bonus points.

Blackjack is, like all poker game, a game of chance. For those who aren’t familiar with the rules, they are fairly simple. You are always playing against the house (the dealer) and no one else, though you might be at a table with more people. Everyone (including the dealer) is dealt one card face up and one face down (which you will look at). When it is your turn, you will have the opportunity to either receive more cards (“hit me”) or stand pat with what you have. The end goal is for you cards to add up to as close to 21 as possible (all face cards are “ten” except Aces, which are either 1 or 11). 

The thing behind Blackjack is that there is always a basic strategy that optimizes your play so that you can win as often as possible. This strategy will only differ with house rules and the number of decks you are playing with, and it can be found almost anywhere online (Wikipedia “Blackjack” for example). Basic Strategy is not all that interesting, though, and you certainly won’t hear any cool casino stories about someone following all the rules they have written on a notecard instead of winning big by taking big risks.

No, the cool thing about Blackjack is that the only way you can beat the house is by, you guessed it, counting cards (perfect Basic Strategy play will still give the house about a 0.5% advantage, whereas card counting can yield the player a 1% advantage). The only problem with card counting is that casinos don’t like it, and you will definitely get kicked out if they catch you doing it. If you’ve ever read Bringing Down the House, the book about the MIT Blackjack team (or seen the horrendous movie-depiction of the book, 21), you’ll know what I’m talking about.

Card counting is about the only interesting mathematical concept related to Blackjack, but it is definitely a skill worth mastering if you have the mind to do it (it requires superb short-term memory and mental math skills). There are different methods of card counting, but the most common way of doing it is probably the simple “Hi-Lo” system, which assigns either a -1, 0, or 1 to every number card in the deck, and the card counter will simply constantly add the assigned numbers together that he sees on the table to assess how “hot” the deck is. Higher cards will generally receive negative numbers, so that when a deck is hot, the card count will be very high (around 11-14), and the card counter will raise his bets accordingly so that he will receive bigger payoffs when the Jacks, Aces, and Kings start rolling in. In reality the MIT Blackjack people worked as a team in a large casino and only one person would do the betting while other people would assess how hot the other tables are. When a table got very hot, they would alert the big-better with a signal of what the count was and he would bet accordingly.

Obviously there are other poker games that are more mathematically interesting on paper (we studied limit hold’em in my Economics Game Theory tutorial last semester), card counting is one of the most practical and easily accessible by those who are good at math but may not be online gambling phenoms. And while we may not be making loads of cash at casino night, maybe some people will come ready to do quick-addition to get some bonus points, because I seriously doubt there will be any bouncers kicking us out like they did in the movie.



  1. At Casino night, card counting will be welcomed and encouraged! Remember, there are real points up for grabs! Unfortunately, roulette and craps, where each play is independent of the last, doesn’t lend itself to counting and the house has an advantage unless you rig the wheel or cause a man-made earthquake or something. (These strategies are not allowed at casino night. Only mathematical cheating is allowed.) Still, some bets are better than others at these games also.

  2. For potential card counters out there, is there any way we could have the particular set of rules that will be played on casino night (# of decks, surrender, double after split, etc.)?

  3. There’s some documents up under “Casino Night” on the website. I agree we should set the answers to these questions ahead of time. We’ll discuss…

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  5. Why do casinos kick out card counters ? As far as I know, it’s not illegal. Do they have the right to do that ?
    Anyway, I think I would never be kicked out, counting cards is too hard for me.

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