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

Card counting, boiled down to the simplest definition, is keeping track of a fluctuating number (usually one single number) that tells you how many high-value cards (10s, face cards, and aces) are left in the deck. If the count is favorable (with lots of those cards left), you make a big bet to leverage the odds of getting dealt a good hand and/or the dealer going bust. If the count is unfavorable (with lots of low cards left), you dial down your bet and ride out the suboptimal deck state. Historically, the very best card counting systems with the most favorable rules (single-deck, strong blackjack odds, strong splitting and double down rules, etc.) provide *just a slight player edge* over the house, in the long run.

The problem with card counting, either online or in real life at most casinos, is the number of decks and the shuffle. Card counting works great, and shaves off a lot of the house edge, when you’re playing single- or double-deck blackjack. But if you’re at a Vegas casino and they’re using a shoe with like 6 decks, it waters down the advantage of card counting. And if they shuffle after every X number of hands or whatever, you never get a very deep deck.

I’ve never played online blackjack, but my default assumption is that most electronic games would shuffle the deck after every hand, since a computer can do it instantly with no downtime. This definitely works against a card counter’s interests.

And also, again, please don’t discount the rules in play, because even the best card counting can’t fight really bad rules. A big part of profiting is from nice 2:1 blackjack payouts, and taking advantage of double downs. So if a game is offering some lower-percentage payout on blackjacks, or doesn’t allow early surrender, or doesn’t let you double down on any hand, the rules are stacked against you.