Tools · Calculator
Risk of Ruin Calculator
Probability of reaching a profit target before losing the bankroll, flat-betting even money.
Bankroll
Bet
Target
Reading the result
Betting $10 at a time, you have a 24.6% chance of turning $500 into $750 before going broke. Larger bets raise that probability because fewer spins means fewer 2.70% tolls; they also make the ride wilder. Try $100 bets against $5 bets to see the effect.
Method and assumptions
Gambler’s ruin with p = 18/37: P(target) = (1 − (q/p)ᵃ)/(1 − (q/p)ᵃ⁺ᵇ), a = bankroll/bet, b = target/bet. Expected duration a/(q−p) − (a+b)·P/(q−p). Flat even-money bets only.