Risk ofRuin Calculator

What is Risk of Ruin?

Risk of Ruin (ROR) is the probability that you will lose your entire bankroll before accumulating enough wins to secure your financial goal.

In sports betting, ROR tells you: given your win rate, average odds, and current bankroll, what's the chance you go broke before you hit your target?

Why ROR Matters

Many bettors have positive EV but still go broke due to variance. ROR quantifies your resilience to losing streaks.

A bettor with 55% edge on -110 odds might have <5% ROR with a 100-unit bankroll but >50% ROR with a 10-unit bankroll. Bankroll size is everything.

The Formula

ROR is calculated using the gambler's ruin formula. It compares your edge (win rate vs. break-even) against your bankroll size:

The formula becomes 1.0 (100% ruin) if your edge is zero or negative.

ROR Benchmarks

• <1%Excellent — very safe bankroll. You can bet aggressively without major ruin risk.
• 1–5%Good — solid bankroll sizing. Most professional bettors target this range.
• 5–15%Moderate — acceptable but thin. A bad streak could hurt. Consider increasing your bankroll.
• 15–40%High — risky. You could lose it all during variance. Increase bankroll or reduce bet size.
• >40%Severe — critical risk. You will almost certainly go broke. Bankroll is far too small.

ROR and Bankroll Management

Never bet the same amount on every bet (flat betting). Instead, use ROR to size your bankroll relative to your edge.

If you calculate <5% ROR, you have room to grow. If it's >15%, reduce bet size or increase bankroll before betting real money.

ROR Limitations

ROR assumes your win rate and odds are constant over time. In reality, edges vary. Use ROR as a guide, not a guarantee.

ROR also assumes you stop when you double your bankroll (or hit a target). In practice, most bettors keep going, so ROR is more of a 'break-even ruin' threshold.