What is Risk of Ruin?
Updated June 2026 · 8 min read
Risk of Ruin is the mathematical probability that you will reach a certain loss percentage — or lose your entire account — given your current win rate, average risk per trade, and account size. It is one of the most underrated concepts in trading.
Many traders think in terms of "my strategy works so I am safe." But even with a profitable strategy, your account is at risk if your risk management is off. Risk of Ruin shows you how large that danger is — in numbers.
Risk of Ruin — the core
Risk of Ruin is the probability that a statistically possible losing streak will cause you to lose your account (or a critical percentage of it), even if your strategy is profitable in the long run.
Why a profitable strategy does not protect you
Suppose you have a strategy with a 50% win rate and 1:2 RR. Positive expectancy — theoretically profitable. But if you risk 5% of your account per trade, how likely is it that you will ever experience a losing streak of 20 trades in a row?
With a 50% win rate, the probability of 10 losers in a row is: (0.5)^10 = 0.1% — seems small. But over 1,000 trades, the chance that this occurs somewhere is many times higher. And 10 losers in a row at 5% risk per trade = 40% loss on your account.
At a prop firm with a 10% max drawdown, this means: your account has failed. Not because your strategy does not work, but because your risk per trade was too large for the statistical variance of your system.
The three factors that determine Risk of Ruin
1. Risk per trade (% of account)
This is the biggest lever. Halve your risk per trade and your Risk of Ruin drops dramatically. The relationship is not linear — the effect of reducing risk is exponentially large. Most professional traders risk 0.5%–2% per trade.
2. Win rate and risk-reward (expectancy)
The more positive the expectancy, the lower the Risk of Ruin. A strategy with a higher win rate or better RR has shorter expected losing streaks, and therefore less chance of reaching a critical drawdown level.
3. The "ruin" threshold
This is the percentage loss you define as "ruin." For prop firms this is the max drawdown (10% at FTMO, 10% at Funding Pips). For personal accounts you choose your own — many traders set 25–30% as their personal stop level.
Practical guidelines for low Risk of Ruin
Rules of thumb per risk level
Conservative — for prop firm challenges and traders in the build-up phase. Risk of Ruin at the 10% threshold is virtually zero with any reasonable strategy.
Standard — suitable for traders with a proven track record (100+ trades). Risk of Ruin is manageable with positive expectancy.
Aggressive — only for experts with very high win rates and generous drawdown margins. Risk of Ruin rises quickly. Not suitable for most traders.
Dangerous — even with positive expectancy, the Risk of Ruin is high enough that long-term survival is unlikely.
Risk of Ruin at prop firms
At prop firms, Risk of Ruin is especially relevant because the ruin threshold is clearly defined: the max drawdown. At Funding Pips this is 10%, at FTMO also 10%. This means that a 10% loss on the account leads to an account reset — your prop firm challenge has failed.
With a daily drawdown limit of 5% (Funding Pips), the math is simple: on one bad day you cannot lose more than 5%. If you risk 2% per trade, this means you stop after 2.5 losers in a row — not because you want to, but because you are forced to.
This is why most experienced prop firm traders risk a maximum of 1% per trade — even if their backtest shows that 2% works. The safety margins at prop firms are narrow, and the price of exceeding them is high (loss of funded account, restarting the challenge).
How do you calculate your own Risk of Ruin?
The exact calculation is complex, but the simplified Risk of Ruin (RoR) formula is:
RoR = ((1 − edge) / (1 + edge)) ^ (threshold / risk_per_trade)
Where 'edge' is your expectancy expressed as a fraction of risk, 'threshold' is the ruin level, and 'risk_per_trade' is the percentage per trade.
In practice, you use an online RoR calculator — but the principle is always the same: smaller risk per trade and higher expectancy = exponentially lower Risk of Ruin.
Monitor your risk per session
Logify tracks how much you risk per day and alerts you as you approach your daily limit. That way you keep your Risk of Ruin low — automatically.
Try Logify free →Conclusion
Risk of Ruin is the mathematical reality behind every trading account. A profitable strategy offers no absolute protection if your risk per trade is too large. The only way to protect your account is to combine small, consistent position sizes with positive expectancy — and never, under any pressure, increase your risk to recover losses.
Frequently asked questions
What % per trade is safe for a prop firm challenge?
With a max drawdown of 10% and a daily limit of 5%, most experienced prop traders recommend 0.5–1% per trade. This gives you a buffer of 5–10 losers in a row without reaching the daily or maximum limit.
Can Risk of Ruin always be calculated?
In theory yes, but you need reliable statistics (minimum 100 trades). With too little data, the calculation gives a false sense of security. Start with conservative risk and adjust once your statistics are stable.
How does Risk of Ruin differ from max drawdown?
Max drawdown is the largest historical decline from peak to trough. Risk of Ruin is the probability of reaching a certain loss percentage in the future. Max drawdown is descriptive (what has happened), Risk of Ruin is probabilistic (what can still happen).