How to Count Cards in Blackjack
A step-by-step guide to the Hi-Lo system - the count professionals actually use.
How do you count cards in blackjack?
To count cards in blackjack, give each card a value (2-6 = +1, 7-9 = 0, 10-Ace = -1), keep a running total as cards are dealt, divide that total by the decks remaining to get the true count, and raise your bet as the true count climbs. It takes practice, not memory.
Card counting has a reputation for genius-level difficulty, largely thanks to films like Rain Man. The reality is far simpler. You are not memorising cards - you are keeping one running number that tells you when the deck has swung in your favour. This guide walks through the Hi-Lo system, the most popular count in the world, one step at a time.
Before you start: learn basic strategy
Counting only adds value on top of perfect basic strategy - the mathematically correct hit, stand, double and split for every hand. Basic strategy alone cuts the house edge to roughly 0.5%. Card counting then tells you when to bet more. Try to count before your basic strategy is automatic and you will simply make expensive mistakes faster. Master the chart first; the count second.
Step 1: Assign a value to every card
In Hi-Lo, every card is worth one of three values:
- 2, 3, 4, 5, 6 - low cards, worth +1
- 7, 8, 9 - neutral, worth 0
- 10, J, Q, K, A - high cards, worth -1
Low cards score +1 because when they leave the shoe, the remaining deck gets richer in high cards - good for you. High cards score -1 for the opposite reason. The count is a running tally of that balance.
Step 2: Keep a running count
Start at zero the moment the dealer shuffles. As each card appears, add or subtract its value. Say the first cards out are K, 5, 3, 9, A, 6. Your running count moves like this: -1, then 0, then +1, then +1, then 0, then +1. Your running count is +1. A positive running count means more high cards remain; a negative one favours the dealer.
Do this for every card on the table - your hand, the dealer's, and every other player's - round after round until the shuffle resets everything to zero.
Step 3: Convert to a true count
Casinos deal from multiple decks to blunt counters, so the running count alone is misleading - a +6 spread across six decks is weak, but +6 with one deck left is strong. Fix this by converting to a true count: divide the running count by the number of decks still to be dealt.
Example: a running count of +8 with about 4 decks remaining gives a true count of +2 (8 ÷ 4). Each +1 of true count shifts the edge roughly half a percent toward you, so a true +2 is about where you cross from underdog to favourite.
Step 4: Change your bets as the count rises
Keeping a count is pointless unless you act on it. The edge comes from a bet spread: small bets when the count is neutral or negative, bigger bets when it is high. A simple ramp is to bet one unit at a true count of +1 or below, two units at +2, three at +3 and so on, up to your table limit and your bankroll's comfort.
Two cautions. First, a wide, obvious spread is exactly what casino surveillance looks for, so keep it disciplined. Second, protect your bankroll: a common rule of thumb is to hold at least 100 times your maximum bet to survive blackjack's natural swings.
How to practice
Build the count in this order. First, count down a single deck card by card until you can reach the end and land on zero (a full deck always nets to zero) in under 25 seconds. Next, deal cards in pairs to force faster addition. Then add true-count conversion by cutting the deck at random depths. Finally, rehearse your bet ramp until raising and lowering bets feels automatic. Short daily sessions beat rare long ones.
Common mistakes to avoid
- Skipping the true count. Betting off the running count in a shoe game gives you a false read of your edge.
- Over-spreading. Jumping from a $10 to a $200 bet the instant the count turns is a red flag to the pit.
- Playing continuous-shuffler tables. A CSM reshuffles every hand - there is no count to keep. Walk away.
- Ignoring basic strategy. The count tells you how much to bet, not how to play the hand. You still need the chart.