Risk of Ruin Calculator

Calculate the probability of losing your entire bankroll given your edge and bet sizing.

Your total gambling bankroll dedicated exclusively to betting.
Your expected win rate advantage over the house. Card counters typically have 1-2%.
Your standard bet amount (one unit).
SD per unit bet. Even-money bets ~1.0, blackjack ~1.15.

Primary Risk of Ruin

Bankroll in Units
Risk of Ruin (Classic Formula)
Risk of Ruin (SD-Adjusted)

Risk at Various Bankroll Sizes

UnitsBankroll ($)Classic RoRSD-Adjusted RoR

Interpretation

Formulas & References:
Classic RoR = ((1 - edge) / (1 + edge))^(bankroll / unit)
SD-Adjusted RoR = e^(-2 × edge × units / SD²)
Sources: Epstein "Theory of Gambling and Statistical Logic"; Schlesinger "Blackjack Attack"