If card counting in blackjack is just keeping track of high cards vs low, does that mean if I could remember all the different cards used (i.e. how many 5s, how many 7s) I would be really good at blackjack?

Question

This would break online casinos because you could easily do that with electronics. Assuming the casino itself is playing fair.

If you could perfectly keep track of how many of which cards are left in the decks, and everytime make the most mathematically sound bet, would the house still have an edge?

(I assume the correct answer will start off saying I don’t understand how card counting works – fair enough, but what about the basic explanation of it did I misinterpret?)

In: Mathematics

Answer 1

You are understanding card counting correctly. You basically track how many ten cards are left in the shoe relative to the total remaining cards in the shoe. When there is a heavy ratio of tens remaining it becomes more common for the dealer to bust, so you increase your bets to take advantage of the favourable situation.

The part everyone seems to be missing is that it’s the increasing your bets that gets you caught. You can’t make large bets every hand or you’ll go bust before the count becomes favorable. But if you bet low and then suddenly jack up your bet size, the casino will notice this and you’ll be asked to leave on suspicion of card counting.

I’ll add a bit of an explanation of expected value (EV) as it’s relevant to card counting. EV refers to the amount of money you stand to gain or lose based on the current odds. In standard blackjack play, the house has I believe a 50.5% win chance if you do everything perfectly. That means that you have a 49.5% chance. That’s a 1% difference, so the EV of every hand (without extra info like card counting can supply) is -1%. In other words, over time, you should expect to lose 1% of your money for every hand you play.

So with card counting, you’re playing hundreds of hands with this -1% rate of return, but because counting gives you access to additional information, you know when the true EV of the hand you’re in is much better than the 50.5/49.5 split that it theoretically is. Maybe you can see that in your current situation the odds go all the way to 55/45 in your favor. Now you’re suddenly getting a positive EV of +10%! That’s when you jack up your bet sizes so that you maximize the positive returns. You only need a few wins before you turn around and losses to that point. But they also train the dealers and the pit bosses to watch for these kind of betting changes which makes you get caught as soon as you succeed.