# ELi5: How does card counting in blackjack work?

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I’ve already tried looking up but just can’t understand it

In: Other

There are a few different systems, but basically it’s a way of keeping track of which cards have already been played so you have some idea of which cards are left in the deck. This is one common system, but the other ones are fairly similar. You start with 0, and every time you see a 2-6 played, you add 1 to the count and every time you see a 10-A, you subtract 1. If you count is positive, that means there are a lot of high cards left in the deck, which statistically benefits you the player. So you should bet more.

For an easier explanation watch the movie ‘21’. That is a story about MIT students who took Vegas for millions.

There is also a Canadian version called ‘The Last Casino’ which also explains it.

In blackjack you make more money by getting exactly 21 with 2 cards (Payout of 3:2 in casinos where card counting is worth doing).

In order to get blackjack you need to draw one of the face cards, so it would be good to improve the odds that you get one. While you can’t change the order the cards come in, you can keep track of how many low cards are left in the deck and how many high cards and bet very little when there’s a lot of low cards and bet a lot when there’s a lot of high cards. By betting a lot when the odds of getting a blackjack are higher, you make up for your losses betting small amounts earlier and hopefully make a small profit at the end.

Card counting is just the way people use to keep track. If you see a low card, add one to the count, and if you see a high card subtract one. At any given point the count is just a measure of how many more high cards there are compared to low cards left to be drawn

There is an episode of This American Life titled “Blackjack” and they sum up the gist of it in the first 5-10 minutes or so. Good episode. Worth a listen.

In short, card counting tracks whether the deck has more high value cards or low value cards. High value cards are better for the player, because the dealer is required to hit on 16 or lower, while the player is free to stand to avoid busting. So counting lets you know when you’re more likely to win, and during those times you bet bigger.

So when counting cards you win bigger and lose smaller.