
Counting cards in Blackjack: The HighLow system
There are many card counting systems that have been devised for
beating Blackjack over the years. One of the best in terms of simplicity
and effectiveness, is the HighLow system, a Blackjack system designed
by Harvey Dubner in 1963. It was called the Point Count system by
Edward Thorp in his second edition of Beat The Dealer (1966), but
it is more generally referred to as the HighLow system, f.e. in
Stanford Wong's Professional Blackjack (1975).
How do you count cards using the HighLow system?
Counting cards using the HighLow system is surprisingly easy. All
you have to do is track one number during a game of Blackjack, the
running count. Suppose the cards are shuffled, and a game of
Blackjack begins. Your running count is then zero. After the first
hand is dealt, you start counting the high and the low cards that
are dealt on each round. In particular, you add or subtract one point
to or from your running count, depending on the cards that are dealt,
and according to the following table:
Ace,King,Queen,Jack,Ten (high cards) 
1 
7,8,9 
0 
2,3,4,5,6 (low cards) 
+1 
If you correctly add and subtract these numbers to, and from, your
running count during a game, your running count gives you an estimate
of the number of high cards that are *not* dealt yet. A positive
running count indicates there are more high cards left in the deck
than dealt already. A negative running count indicates there are
more low cards left in the deck than dealt already.
Vary your bet size according to your running count
Keeping a running count is easy to do, as we demonstrated in the previous
paragraph. However, it wouldn't do you any good if you didn't vary
your bet size according to your running count. Computer simulations,
originally done by Edward Thorp, have shown that a deck with a large
percentage of high cards (10A) left, is favorable to the player.
For example, with many high cards left the chances of getting a Blackjack
are higher. A positive running count indicates that the deck contains
more high cards than low ones. You should therefore raise your bet
size, when your running count gets higher.
Edward Thorp's simple point count system can be summarized as follows:

Always play basic strategy (more information on
basic strategy can be found here). 

If your running count is zero, or negative, only bet one unit. 

If your running count is positive, bet as many units as your
running count total. 
Refinement of the simple point count system: calculating the true
count
There are many Blackjack variants available today. One important feature
that distinguishes one Blackjack game from another, is the number
of decks from which the cards are dealt. Singledeck Blackjack is
increasingly hard to find, and Blackjack with four or more decks is
much more common.
The simple point count system described above, doesn't take into
account how many cards there are left in the shoe. As you can imagine,
if your running count is +4, it makes a whole lot of difference
whether there are 26 cards left in the shoe, or for example 208.
Generally speaking, a positive running count is worth less to you,
the more cards there are left in the shoe. If you would use the
simple point count system in a Blackjack game with four decks or
more, *without* adjusting your running count for the number of cards
left in the shoe, you're headed for disaster.
Fortunately, this problem is solved easily by calculating the
true count. The true count is based on your running count *and*
the number of cards that are left in the shoe. To be more precise,
the true count is your running count divided by the number of decks
that haven't been dealt yet. An example will illustrate what consequences
this should have for your bet size: if we compare singledeck Blackjack
with twodeck Blackjack, and assume the game has just begun, and
the running count is +4, you would bet 4 units in the singledeck
game, but only 4/2=2 in the twodeck game. The running count in
both games is +4, but the true count in the twodeck game is +4
divided by 2, because there are approximately two decks left to
be dealt.
Refinement of the simple point count system: deviations from basic
strategy
In all calculations and examples above, we've assumed you are playing
basic strategy. However, you can gain an additional (small) advantage
if you deviate from basic strategy in special cases, depending on
your running count (or better your true count). When the true count
becomes high, you should stand more, double down more and split more,
than prescribed by basic strategy (the opposite is true when your
true count becomes negative). In fact we could give you a table for
each true count, that described the correct deviations from basic
strategy. This is however beyond the scope of this article. Also keep
in mind that deviating from basic strategy in general only marginally
improves your advantage. If you're really interested in this subject,
we advise you to consult Professional Blackjack, a good book on this
subject, written by Stanford Wong.
Remember Blackjack card counting only works in landbased casinos
and *not* in online casinos, because in an online casino the deck
is reshuffled after each round.
Tip: Both Cryptologic
and Boss Media offer a single
deck Blackjack game. The house edge on the former approaches zero,
and on the latter it's actually slightly in favor of the player.
Microgaming offers a variety
of Blackjack variants, ranging from two to eight decks.

