Risk of ruin is the probability that a trader will lose enough capital to be unable to continue trading. It is a statistical measure that combines your win rate, average risk-reward ratio, and risk per trade to determine the likelihood of catastrophic loss. Understanding risk of ruin is essential because even a profitable strategy can blow your account if your position sizing is wrong.
How Risk of Ruin Works
Risk of ruin answers the question: “Given my win rate, my average win/loss ratio, and how much I risk per trade, what are the chances I’ll lose so much money that I can’t recover?”
The concept is based on probability theory. Even a strategy with a 60% win rate will experience losing streaks. If your position sizing is too aggressive, a normal losing streak can wipe out your account before the strategy’s edge has time to play out.
The Risk of Ruin Formula
The simplified formula:
Risk of Ruin = ((1 - Edge) / (1 + Edge)) ^ Capital Units
Where:
- Edge = (Win Rate × Avg Win/Avg Loss) - (1 - Win Rate)
- Capital Units = Account size / Risk per trade
Example
- Win rate: 50%
- Average win: $200, Average loss: $100 (2:1 R:R)
- Edge = (0.50 × 2) - 0.50 = 0.50
- Risking 2% per trade on a $10,000 account = 50 capital units
- Risk of Ruin = ((1 - 0.50) / (1 + 0.50))^50 = (0.333)^50 = essentially 0%
Same strategy, but risking 10% per trade = 10 capital units:
- Risk of Ruin = (0.333)^10 = 0.002% (still very low with a strong edge)
Now with a weaker edge — 45% win rate, 1.2:1 R:R:
- Edge = (0.45 × 1.2) - 0.55 = -0.01 (negative expectancy)
- Risk of ruin: 100% — a negative expectancy strategy guarantees ruin regardless of position sizing.
Risk Per Trade: The Survival Lever
| Win Rate | R:R | Risk/Trade | Risk of Ruin |
|---|---|---|---|
| 50% | 1.5:1 | 1% | Under 1% |
| 50% | 1.5:1 | 2% | Under 1% |
| 50% | 1.5:1 | 5% | ~5% |
| 50% | 1.5:1 | 10% | ~25% |
| 50% | 1.5:1 | 20% | ~55% |
The same strategy goes from near-zero risk of ruin to coin-flip survival odds just by increasing risk per trade from 1% to 20%. This is why position sizing is more important than strategy.
Why Traders Blow Accounts
Most account blowups aren’t from bad strategies — they’re from excessive risk per trade. Common triggers:
- Revenge trading — Doubling position size after a loss
- Overconfidence after wins — Increasing risk during winning streaks
- Ignoring position sizing — Trading “by feel” instead of by percentage
- News gambling — Taking oversized positions before major events
All of these increase risk per trade, which directly increases risk of ruin.
Tracking Risk of Ruin in Your Journal
Your journal should track:
- Average risk per trade — Is it staying within your defined limit?
- Maximum risk per trade — Have you ever exceeded your limit? When and why?
- Risk consistency — Standard deviation of your risk percentage (lower = safer)
- Estimated risk of ruin — Recalculated monthly based on your actual win rate, R:R, and risk per trade
PipJournal tracks your risk per trade on every position and alerts you when you deviate from your defined risk parameters — helping you maintain the discipline that keeps risk of ruin near zero.
