Level 7 · Lesson 8 of 16 · 6 min read
Risk of Ruin: Why Overleveraging Kills Trading Accounts
The mathematical proof that small risk per trade is the only path to survival.
Researched and written by Laurent Casino math: At 1% risk per trade, your account is the casino. At 10% risk per trade, your account is the gambler. Casinos stay open for decades. Gamblers go broke in hours. The only difference is the size of the edge and the size of each bet relative to the bankroll.
What "Ruin" Means in Trading
Ruin is reaching a drawdown level from which you cannot or will not recover. For most traders, losing 50% of their account effectively ends their trading career: the mathematical recovery is too hard and the psychological damage is too deep.
Risk Per Trade and Ruin Probability
| Risk per Trade | Win Rate 40% | Win Rate 50% | Win Rate 60% |
|---|---|---|---|
| 1% | ~0% | 0% | 0% |
| 2% | ~2% | ~0% | 0% |
| 5% | ~25% | ~12% | ~3% |
| 10% | ~55% | ~40% | ~20% |
| 20% | ~85% | ~70% | ~50% |
Approximate ruin probabilities assuming 1:2 risk-reward over 500 trades, ruin defined as 50% drawdown.
The numbers are stark. At 1% risk, it's almost impossible to reach ruin regardless of win rate. At 10% risk, there's a 40% chance of ruin even with a coin-flip win rate. At 20% risk, even a 60% win rate gives you a 50% chance of ruin.
Why People Overtrade Size Anyway
If the math is so clear, why do traders still risk 5-10% per trade? Three reasons:
- Greed: "If I risk 10%, I'll make 20% per winning trade!" True, but you'll also lose 10% per losing trade, and your losing streaks will destroy you.
- Impatience: "1% risk is too slow. My $2,000 account will take forever to grow." Growing slowly is infinitely better than losing quickly.
- Overconfidence: "My strategy is really good, so I don't need small risk." Every strategy has drawdowns. No strategy is exempt from the math of ruin.
The professional perspective: Prop trading firms, hedge funds, and institutional desks all enforce strict risk limits per trade and per day. If the best-funded, most sophisticated traders in the world use strict risk limits, a retail trader with a $5,000 account has no business risking 10% per trade.
Key Takeaways
- • Probability of ruin = the chance of losing enough capital that recovery is impossible.
- • At 1% risk per trade, probability of ruin is near zero for any strategy with positive expectancy.
- • At 5% risk, probability of ruin becomes significant even with a 50% win rate.
- • At 10% risk per trade, you're gambling, not trading.