Blackjack counting systems
Card counters give certain point values - either positive (+), negative (-) or neutral (0) - to each card in play. Each deal card influences the count depending to its value. Low cards tend to increase the count as they offer better probabilities of receiving high cards, while high cards, consequently, decrease the count.
Different blackjack counting systems offer different approaches to counting and assessment of cards due to their efficiency in a game. Here you can read about some of the most popular blackjack counting systems.
Hi-Lo counting system
Hi-Lo counting system (other names include High-Low or Plus-Minus system) was developed in the 1960s basically for single-deck games and doesn't work as well with the multiple-deck games now common in most casinos. It is considered to be the simplest system of blackjack card counting and is often recommended for beginners.
According to the Hi-Lo count, each card in play is assigned a certain point value. It is +1 for the cards from 2 to 6, "0" for cards from 7 to 9 that have no effect on the count and -1 for high cards like 10, Jack, Queen, King and Ace. As the Hi-Lo system is balanced, the total sum of all card point values equals zero.
KO (Knock-Out) blackjack counting system is one of the most popular unbalanced counting systems. The total sum of card point values doesn't make a zero with this system applied. The count generally goes like in Hi-Lo system with an extra card assessed at +1 - seven. As far as there are four Sevens in a single-deck blackjack game, the total of values is +4 instead of "0" with Hi-Lo Count. This imbalance is aimed at simplifying the game process by means of avoiding conversions of "running count" into "true count". Just as the KO system sounds rather easy to apply, it is far less accurate and profitable.
Hi Opt I
Hi Opt I (Highly Optimum or Einstein Count) is a counting system developed mainly for advanced players. The system works basically the same as Hi-Lo System but offers additional rules and changes in assigning point value. It provides slight increase in player's advantage and is altogether more advanced. In Hi Opt 1, card point values are +1 for cards from 3 to 6, -1 for all 10-valued cards and "0" for 2, 7, 8, 9 and Ace.
Hi Opt II
Hi Opt II is a more advanced variation of Highly Optimum card counting strategy offering a very slight increase of player's advantage. It actually requires high level of concentration during the game. The matter is that with Hi Opt II system applied some cards get the point value of 2. Twos, threes, sixes and sevens are scored +1, fours and fives get the value of +2, eights, nines and Aces are neutral and get point value of "0", and 10-valued cards get the value of -2. There are certain blackjack variations concerning Aces that are not entirely neutral, which only complicates applying the system.
Red 7 Count
According to the Red 7 unbalanced counting system, card point values are +1 for cards from 2 to 6, -1 for the 10-valued cards and Ace and "0" for 8 and 9. There is a unique rule concerning the Sevens, according to which red Sevens are scored +1 and black Sevens get a value of "0". No need for true count conversion makes this otherwise over-complicated system work faster.
Wong Halves system
Wong Halves includes 0.5 values in the count, which makes it one of the most complicated balanced blackjack counting systems. At the same time it is possibly the most accurate system using true count to calculate player's advantage. Threes, fours and fives get a value of +1, nines and ten-valued cards are counted -1, twos and sixes get a value of +0.5, +1.5 is for fours, and -0.5 for eights.