Risk of ruin is one of the most important — and most overlooked — concepts in trading. It tells you the probability that your trading strategy will eventually lose enough money to wipe out a significant portion of your account.
What Is Risk of Ruin?
Risk of ruin is the statistical probability that your account will drawdown to a specified level (the “ruin threshold”) given your:
- Win rate — how often your trades are profitable
- Risk per trade — how much of your account you risk on each trade
- Reward:Risk ratio — your average winner size relative to your average loser
- Ruin threshold — the drawdown level you consider “ruin” (commonly 50%)
Even a profitable strategy can blow up if position sizes are too large relative to the edge.
The Risk of Ruin Formula
Risk of Ruin = (Loss Rate / (Win Rate × R:R))^(Threshold / Risk Per Trade)
Breaking It Down
- Loss Rate / (Win Rate x R:R) — this ratio must be less than 1 for the strategy to have an edge. The further below 1, the stronger the edge.
- Threshold / Risk Per Trade — this is the number of “units” of risk between your current balance and ruin. More units means more protection.
The formula raises the edge ratio to the power of the number of risk units. A small edge ratio raised to a large power produces a very small risk of ruin.
Why Risk of Ruin Matters
Example 1: Safe Strategy
- Win Rate: 55%, Risk Per Trade: 1%, R:R: 2.0, Ruin Threshold: 50%
- Risk of Ruin: Virtually 0%
- This trader would need to be extraordinarily unlucky to blow up
Example 2: Dangerous Strategy
- Win Rate: 45%, Risk Per Trade: 5%, R:R: 1.5, Ruin Threshold: 50%
- Risk of Ruin: ~29.5%
- Nearly 1 in 3 chance of losing half the account — unacceptable
The difference? Position sizing. Trader 2 risks 5x more per trade, and their edge is thinner.
How Position Size Affects Risk of Ruin
The single biggest lever for reducing risk of ruin is position size. Consider a strategy with 55% win rate and 2:1 R:R:
| Risk Per Trade | Risk of Ruin (50% threshold) |
|---|---|
| 0.5% | ~0.00% |
| 1% | ~0.00% |
| 2% | ~0.07% |
| 5% | ~4.5% |
| 10% | ~21% |
The relationship is exponential — doubling position size doesn’t double risk of ruin, it can increase it by 10x or more.
Consecutive Losses and Ruin
The calculator also shows the maximum number of consecutive losses needed to reach your ruin threshold. This helps you prepare psychologically:
- At 1% risk: 50 consecutive losses to hit 50% drawdown
- At 2% risk: 25 consecutive losses
- At 5% risk: 10 consecutive losses
- At 10% risk: 5 consecutive losses
While 50 consecutive losses is nearly impossible, 5 in a row is quite common. This is why risk management rules exist.
Professional Risk of Ruin Standards
Most professional trading firms and fund managers require:
- Risk of ruin below 1% before allocating capital to a strategy
- Risk per trade of 0.5-2% maximum
- Minimum 500 trades of historical data to validate win rate and R:R
If your calculated risk of ruin is above 5%, you should reduce your position size before trading live.
Common Mistakes
- Overestimating win rate — Backtest results often overstate real-world performance. Use conservative estimates.
- Ignoring correlation — If you trade multiple correlated positions, your effective risk per trade is higher.
- Changing position size after losses — Increasing risk to “make back” losses dramatically increases ruin probability.
- Using too high a ruin threshold — A 50% drawdown requires a 100% return to recover. Consider using 25% as your threshold.
How JournalPlus Helps
You just calculated your risk of ruin using estimated inputs. But your real win rate and R:R ratio change over time — and if they deteriorate without you noticing, your ruin probability spikes silently.
JournalPlus calculates your risk of ruin from actual trading data and updates it after every trade. When your risk metrics start deteriorating — a dropping win rate, shrinking R:R, or a growing losing streak — you get alerted before the damage compounds. You’ll know your real survival probability, not a one-time estimate from a calculator.
One calculation tells you where you are. Continuous monitoring keeps you alive.
