How does card counting work in blackjack?

Card counting is the most famous idea in blackjack, and also the most misunderstood. It is not memorizing every card - it is a simple running score that tells you when the deck has tilted in your favor so you can bet bigger at the right moments.

Quick answer: Card counting keeps a running tally of the cards already played to estimate whether the remaining deck is rich in high cards or low cards. High cards (tens and Aces) favor the player, so a counter bets more when the count is high and less when it is low. It is legal skill, not cheating, but it does not work against online shuffling.

The idea behind counting

A deck loaded with tens and Aces helps the player: more blackjacks, better doubles, and a dealer who busts more often. A deck full of low cards helps the dealer. Counting simply measures which situation you are in right now.

The Hi-Lo system

In the popular Hi-Lo system, cards 2 through 6 count as +1, 7 through 9 count as 0, and 10s and Aces count as -1. You keep a running total as cards appear, then divide by the number of decks left to get a 'true count.' A high true count means bet more; a low one means bet the minimum.

Legal, hard, and limited

Counting is a legal mental skill, but casinos can ask skilled counters to leave, and it takes practice to do accurately at speed. It also only works when cards are dealt from a shrinking shoe - it fails completely against the constant reshuffling used online. Build your foundation with solid basic strategy first.

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Related questions

Can you count cards in online blackjack?

Almost never. Online blackjack games, including ours, typically reshuffle the full deck before every single hand. Card counting depends on tracking cards as a shoe is dealt down over many hands, so a shuffle after each hand resets the count to zero and makes it useless. Counting only works when the same shoe is dealt through several hands.

Should you take insurance in blackjack?

For almost everyone, no. Insurance is a side bet offered when the dealer shows an Ace, wagering that their hidden card is a ten. It pays 2 to 1, but the dealer completes a blackjack less than a third of the time, so the bet loses money over the long run. Only card counters can occasionally beat it.

What is the house edge in blackjack?

The house edge is the small built-in advantage the casino holds over time. In a good blackjack game played with correct basic strategy, it is only about 0.5% - one of the best odds in any casino. Poor rules like 6-to-5 blackjacks, and common player mistakes, can push the real edge to 2% or more.