Blackjack possibly has the lowest house edge of any casino table games, with an edge as low as a 0.28% in favor of the house.
Counting cards is used to lower the house’s edge, or even give the player an edge over the casino. The player edge may range between 0%-1% when counting cards.
The Hi-Lo strategy
The most popular card counting strategy is the “Hi-Lo strategy”, primarily because it is simple to master and yields good results.
With this strategy high cards are given a value of -1, while low cards are given a a value of +1. When added up, they total the running count. Bet amount is placed based on the running count – bets increased when the count is positive and decrease or not placed when the count is negative.
The reason the “Hi-Lo strategy” works is because high cards (10 to Ace) improve the player’s chances of hitting a blackjack, which pays out at 3:2. They also increase the dealer’s chances of going “bust” – since they have to hit on 16 and under. Low cards, on the other hand, are bad for the player – reducing his chances of getting a blackjack, but good for the dealer by decreasing his chances of busting on 16 or under.
If the high to low card ratio is higher than normal – meaning, there are lots of high cards still in the deck, the player can place a bigger bet to increase the amount he stands to win.
The running count
To track high to low card ratio, cards are assign a value between -1 to 1.
Cards 2-6 have a value of +1.
Cards 7-9 have a value of 0.
Cards 10-Ace have a value of -1.
The count starts at 0 every time the decks are reshuffled, and each time a card comes out, it’s value is added to the tally.
Factor in the decks
To get an accurate running count, one must take into account the number of decks left to be dealt.
In order to factor in the number of decks one would have to divide the running count by the number of decks waiting to be dealt. If your running count is +6 and there are 3 decks left, the real count is actually +2.
Bets are increased when the count is running positive, meaning +2 and above.
Generally speaking, one would want to increase their bet by one unit for each point that the tally goes up.