Card counting is a mathematical strategy employed in blackjack to track the composition of the remaining deck. Unlike common misconceptions, card counting is not cheating—it is a legitimate analytical technique that uses publicly visible information to calculate odds. The practice gained widespread attention in the 1960s when MIT students developed systematic approaches to advantage play.
The basic principle behind card counting involves assigning numerical values to cards. Low cards (2-6) are assigned positive values as they favor the dealer, while high cards (10-Ace) receive negative values as they benefit the player. By maintaining a running count throughout play, skilled players can estimate whether the remaining deck composition favors hitting, standing, or increasing bet sizes. The most popular systems include the Hi-Lo method, Omega II, and the Zen Count.
Historical card counters employed the Hi-Lo system extensively during the 1970s and 1980s. This system assigns +1 to cards 2-6, 0 to cards 7-9, and -1 to cards 10-Ace. Players track the "true count" by dividing the running count by estimated remaining decks. Understanding penetration—the percentage of the deck dealt before reshuffling—is crucial for effective counting accuracy.