Card counting
How to Count Cards in 21: A Beginner's Step-by-Step Guide
Card counting is simple arithmetic: +1, 0 or −1 for every card you see. Here is the whole method, one card at a time.
Why counting works
In 21, the cards that have been played are gone until the next shuffle. That makes each hand depend on the ones before it — unlike roulette or dice, where every spin starts fresh.
High cards (tens and Aces) help you: they make blackjacks, which pay you 3:2 while the dealer's are only even money, they make your doubles succeed, and they bust the dealer, who must hit stiff hands. Low cards (2 to 6) help the dealer. Counting is simply keeping track of which kind is left in the shoe, and betting more when it is rich in high cards.
Step 1: Learn the Hi-Lo values
Hi-Lo is the most widely used counting system and the best one to learn first. Every card gets one of three values:
| Cards | Hi-Lo value | Why |
|---|---|---|
     | +1 | Low cards leaving the shoe is good for you |
   | 0 | Neutral — ignore them |
     | −1 | High cards leaving the shoe is bad for you |
There are five low values and five high values per suit, so a complete deck adds up to exactly zero. That is what makes Hi-Lo a balanced count, and it gives you a built-in way to check yourself: count down a full deck and you should finish on 0. Our counting systems chart compares Hi-Lo with Hi-Opt I, KO and the others.
Step 2: Keep a running count
Start at 0 after the shuffle. As each card is turned over, add its value. The total you carry is the running count. Here are twelve cards as they might fall in a round, with the value of each card and the running count after it:
- +1+1
- −10
+1+1
0+1- +1+2
−1+1
+1+2
−1+1
+1+2
0+2
0+2
−1+1
Card valueRunning count
Twelve cards later the running count is +1: slightly more low cards than high cards have gone. Now a round from later in the shoe, when a lot of small cards have been dealt:
+1+4
+1+5
+1+6- +1+7
0+7
+1+8- −1+7
+1+8- +1+9
Card valueRunning count
Starting from +3, this round pushes the running count to +9. The remaining cards are now rich in tens and Aces — a good time to have a bigger bet out.
Step 3: Convert to a true count
A running count of +9 means much more with one deck left than with five, because those extra high cards are concentrated into fewer cards. To compare like with like, divide by the number of decks still to be dealt:
True count = running count ÷ decks remaining
| Running count | Decks left | True count |
|---|---|---|
| +9 | 4.5 | +2 |
| +9 | 1.5 | +6 |
| +6 | 3 | +2 |
| −4 | 4 | −1 |
Estimate the decks remaining by glancing at the discard tray: if two of six decks are in it, four are left. Rounding to the nearest half deck is accurate enough. In a single-deck home game you can skip this step almost entirely.
Step 4: Bet with the count
The count only earns money when you act on it. Each point of true count is worth roughly half a percent to the player. The house starts with an edge of about 0.5%, so in a typical six-deck game the advantage swings your way at a true count of around +1 to +2.
A simple starting bet ramp, in betting units:
| True count | Bet |
|---|---|
| +1 or lower | 1 unit (table minimum) |
| +2 | 2 units |
| +3 | 4 units |
| +4 | 6 units |
| +5 and up | 8 units |
The count can also change how you play a hand. The best-known example: take insurance when the true count is +3 or higher — the one time that side bet is worth making. The complete card counting guide covers these strategy deviations and how much bankroll a count needs.
How to practise
- Learn the values cold. Flip through a deck one card at a time saying the value aloud. Aim for a full deck in under 30 seconds, finishing on 0.
- Count in pairs. Flip two cards at a time and give the combined value.
- Add speed and distractions. Use the trainer at dealing speed, then with the TV on.
- Practise the true count. Convert at random points in a multi-deck shoe.
- Play full hands. Keep the count while making correct basic strategy decisions at the same time.
Then move on to the blackjack game, which can show a live running count so you can check yourself hand by hand.
Is it legal?
Yes. Counting cards in your head is legal — you are using information every player at the table can see. Using a device or software to help you count at a casino is illegal in many places.
Casinos are private businesses, though. A player they suspect of counting may be limited to flat bets, asked to stop playing blackjack, or asked to leave. Most online blackjack also reshuffles after every hand, which makes counting impossible there. Counting is the foundation of winning at 21; if you would rather not count at all, read how to win at blackjack without counting cards.
Frequently asked questions
How long does it take to learn to count cards?
Most people learn the Hi-Lo values in an afternoon. Counting a full deck quickly and accurately takes a few weeks of daily practice, and doing it under casino conditions takes longer.
Is counting cards illegal?
No. Counting cards in your head is legal — you are only paying attention to cards that are dealt face up. Casinos are private businesses, though, and may ask a player they suspect of counting to stop playing blackjack or to leave. Using a device to count is illegal in many places.
Does card counting work online?
Not against most online blackjack, which reshuffles after every hand, so there is nothing to track. It can work in live-dealer games dealt from a shoe that is not shuffled after each round.
What is the easiest card counting system?
Hi-Lo is the standard starting point: three values, balanced so a full deck counts back to zero. KO is similar and avoids the true count conversion, at the cost of some accuracy.
What is a good true count?
In a typical six-deck game the player starts to have the edge at a true count of roughly +1 to +2. Each additional point is worth about half a percent.
Sources
Rules and figures in this article are taken from Wikipedia:
- Card counting — Wikipedia
- Blackjack — Wikipedia