Bankroll Survival Calculator
How long a bankroll survives, and the chance of reaching a win target before it runs out. This uses the gambler's-ruin formula rather than a simulation, so the numbers are exact for the model.
Risk of ruin by session length
| Session length | Turnover | Expected cost | Chance of busting |
|---|
Ruin probabilities in this table use a random-walk approximation and are accurate to within about a percentage point for realistic bankrolls. The headline figures above are exact.
Why longer sessions are worse sessions
With a negative edge, time is not neutral. Each spin adds a small expected loss, so the longer you sit, the further the distribution shifts against you. A short session has high variance and can easily end in profit; a long one converges on the expected result, and the expected result is a loss.
This inverts the usual advice about patience. In investing, time is an ally because the expected return is positive. In roulette the expected return is negative, so the mathematically optimal session length is the shortest one that still gives you what you came for.
Small targets are usually reached
Set the target to a tenth of your bankroll and the calculator will show a high success rate — often above 85%. That is not an edge. It is the structure of a random walk with absorbing barriers: you frequently win a little and occasionally lose everything, and the two exactly cancel out plus the house's cut. The strategy simulator shows the same effect from the other direction.
How to use the Bankroll Survival Calculator
- Choose the wheel.
- Enter your bankroll and a flat bet per spin on an even-money bet.
- Enter the profit you would be happy to walk away with.
- Read the chance of reaching the target before going broke, and the expected number of spins either way.
Worked example. $500 bankroll, $10 bets on red, European wheel. Target +$500: about a 6.3% chance of reaching it first. Target +$50: about 75%. Small targets are usually reached and large ones rarely are — the rare losses are what make the average a loss.
GETRAKEBACK. 18+.
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18+. Roulette has a fixed house edge, so over enough spins the maths favours the operator — always. If you play for real, treat it as money spent on entertainment, set a limit before you start and stop when you reach it. Our responsible gambling page covers the warning signs and where to get free, confidential help.