Learn Card CountingCard counting bet sizing and bankroll
Updated
Why bet sizing is the real engine
Your count tells you when the odds are better. Bet sizing is how you profit from it. If you bet the same amount every hand, you’d still be roughly even with the house or slightly behind, because the favorable hands are outweighed by the unfavorable ones. When you bet more on good hands and less on bad ones, your average edge turns positive.
The edge is small
A rough rule of thumb for Hi-Lo: the player’s edge is approximately 0.5% × (true count − 1) under typical multi-deck rules. At a true count of +1 you’re roughly even with the house. At +2, you have about a 0.5% edge. At +5, about 2%. And at negative counts, the house edge increases, which is why counters bet the minimum there.
Two percent doesn’t sound like much, and it isn’t: on a $100 bet you expect to win about $2 on average, but any single hand ends in a loss of $100, a push, a win of $100 or $150 for a blackjack, or even $200 or more either way when you double or split.
What a bet spread is
A bet spread is the range between your smallest and largest bets, for example $10 to $100 would be a 1-to-10 spread. A wider spread captures more of the edge but also is more visible and requires a bigger bankroll. A narrow spread (say, 1-to-4) is safer and less profitable.
A simple illustration (not advice): say your minimum is $10. At a true count of +1 or lower you bet $10. At +2 you bet $20, at +3 you bet $30, and so on, up to a cap. The bet grows in proportion to your advantage.
Variance: why even a winning player loses a lot
Blackjack outcomes swing widely. One hand has a standard deviation of a bit over one bet. After 100 hands of $10, the standard deviation is about 1.15 × $10 × √100 ≈ $115, much larger than the expected profit of a few dollars. So after 100 hands, a break-even or losing session is quite normal, even for a winning counter. Over thousands of hours, results converge toward the expected value, but you must survive the swings to get there.
Bankroll
Your bankroll is the money you set aside for this, and it must be money you can afford to lose entirely. Many players who study this suggest a bankroll of roughly 100 to 200 times their largest bet to keep the odds of going broke fairly low. With a $100 maximum bet, that’s $10,000 to $20,000. That is a lot of money to put at risk for a thin edge, which is why most people should treat counting as a hobby and a challenge, not an income plan.
Risk of ruin, simply
Risk of ruin (RoR) is the probability that you lose your whole bankroll before you reach some large target. It depends on three things:
- Your edge: more edge lowers the risk.
- Your variance: wilder swings raise the risk.
- Your bankroll relative to your bets: a bigger cushion lowers the risk.
Think of it like a boat on a rough sea with a slight tailwind. A small boat (small bankroll) can capsize before the wind helps; a bigger boat will probably make it. There is no bankroll that makes it risk-free.
Betting fractions of your bankroll
A well-known principle called the Kelly criterion says that the optimal bet size is proportional to your edge divided by the variance. With a 1% edge and a variance of about 1.3 per unit, Kelly suggests about 0.77% of your bankroll on that hand. Many counters bet a fraction of Kelly (half or less) because it dramatically reduces the swings in exchange for a small loss of growth.
Practical, honest advice
- Treat it as entertainment first. Expect to lose money in some sessions.
- Set loss limits before you sit down and stick to them.
- Don’t chase losses. Larger bets after a loss is the fastest road to ruin.
- Know your table’s rules. Poor payouts (like 6:5 blackjack) erase the edge entirely.
When you’re ready, review basic strategy, since mistakes in play cost more than most beginners realize.