Most traders focus entirely on their strategy's win rate and ignore whether that win rate is actually enough to survive a funded account challenge. Risk of ruin (RoR) is the most important number in prop trading. It tells you the probability your account hits max drawdown before reaching the profit target. If it's above 10%, reconsider before paying for a challenge.
What is risk of ruin?
Risk of ruin (RoR) is the probability that a sequence of losing trades wipes out a defined portion of your account before you reach your goal. In prop trading, "ruin" means hitting the firm's maximum drawdown limit.
Win rate: 55% · R:R ratio: 1.5 · Risk per trade: 1% · Max DD: 10%
RoR = ((1 − 0.55) ÷ 0.55) ^ (10 ÷ 1) = (0.818) ^ 10 ≈ 13.5%
That means roughly 1 in 7 traders with these exact stats will fail the challenge purely due to variance.
How to reduce your risk of ruin
There are three levers. Each one independently reduces RoR:
- Lower risk per trade — dropping from 1% to 0.5% dramatically reduces RoR because it increases the number of losing trades you can absorb
- Improve win rate — even small improvements compound significantly in the formula
- Improve R:R ratio — taking trades with better reward relative to risk reduces the damage each loss causes
| Win rate | R:R | Risk % | RoR (10% max DD) | Verdict |
|---|---|---|---|---|
| 45% | 2.0 | 1% | ~8% | Borderline |
| 50% | 1.5 | 1% | ~10% | Acceptable |
| 55% | 1.5 | 1% | ~4% | Good |
| 55% | 1.5 | 0.5% | ~0.2% | Excellent |
| 60% | 2.0 | 1% | ~0.6% | Excellent |
Profit factor and expected value
Expected value (EV) per trade tells you if your strategy makes money long term:
Example: (0.55 × 1.5) − 0.45 = 0.825 − 0.45 = +0.375% per trade
Any positive EV means profitable long term. But positive EV alone doesn't mean you'll survive a challenge — RoR tells you the short-term variance risk.
Profit factor = Gross wins ÷ Gross losses. A profit factor above 1.5 is considered solid for prop trading. Below 1.2 and your edge is too thin to reliably survive challenge variance.
Free risk of ruin calculator for prop firm traders
Enter your win rate, R:R ratio and risk % — get your risk of ruin, profit factor and expected value before spending a cent on a prop firm challenge.
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