Bankroll Management & Variance for Blackjack Players
Even perfect play loses sometimes. Variance is how often, and how badly. Bankroll is how you survive it.
If basic strategy gives you a 0.5% house edge, you'd expect to lose $0.50 per $100 bet. That's the average across millions of hands. In any one session, you're at the mercy of variance.
Standard deviation per hand
Blackjack has a per-hand standard deviation of about 1.15 betting units. Over 100 hands, the SD of your result is √100 × 1.15 ≈ 11.5 units. That's how much your bankroll can swing on luck alone.
Sizing the bet
A common rule: never bet more than 1% of your bankroll on a single hand. That keeps the risk of ruin small even through bad runs.
Why session length matters
Short sessions are dominated by variance — you can play perfectly and lose. Long sessions are dominated by edge — bad players lose, perfect players lose less. Practice mode shows you the difference between actual P/L and EV-adjusted P/L for exactly this reason.