You don’t have to be an autistic savant or an MIT graduate student to know how to count cards. All you need is the ability to add, subtract, and divide.
Although there are different systems for card counting, the one I use is called Hi-Lo. This system assigns secondary values to each card that you then add or subtract in order to calculate what is called the “Running Count”. Simply put: if you see 2-6, you add one and if you see 10-A, you minus 1. That’s it.
[2;3;4;5;6] = +1
[10;J;Q;K;A] = -1
[7;8;9] = 0
A great way to practice looking at cards for the Running Count is taking a whole deck of cards and then counting every card (using the secondary values) until you get to the last card. When you get to the last card, see if you can use the Running Count to determine whether or not the card is a +1, -1, or 0 valued card.
So how do card counters use the Running Count to their advantage? The general idea is that they bet high when the count is high and bet small (or not at all) when the count is negative. The mathematics behind this has to do with the Expected Value of playing Blackjack when the deck is rich with 10’s and Aces. The simple way to explain it is that you’re more likely to be dealt blackjack and 20’s and the dealer is more likely to bust when showing bust cards. Note that you aren’t guaranteed to win these hands; you just have a higher expected value for the bet you place. Having a 1-2% edge over the house doesn’t seem like much, but in the long term over a large sample size… this makes a big difference. See my previous entry on Expected Value to see what I’m talking about.
If you’ve managed to stay with me so far, you might have some questions like “How much do I increase my bet based on the Running Count?” “I thought you said we needed to know how to divide, I haven’t seen that yet!” All this will be covered in my next entry, Card Counting: Advanced.