Drawdown and Risk of Ruin: The Maths of Staying in the Game

Most traders track returns. The number that actually decides whether they are still trading in two years is drawdown — how far the account falls from its peak before it recovers.

The recovery asymmetry

Losses and gains are not symmetric. Lose 10% and you need 11.1% to get back. Lose 50% and you need 100%. Lose 80% and you need 400% — a five-fold return simply to break even.

• •−10% → +11% to recover
• •−25% → +33% to recover
• •−50% → +100% to recover
• •−75% → +300% to recover
• •−90% → +900% to recover

This is why capital preservation beats return chasing. Avoiding one catastrophic drawdown is usually worth more than several good years of extra performance.

Losing streaks are longer than you think

With a 50% win rate, the chance of eight consecutive losses in any given eight trades is about 1 in 256. That sounds remote — until you take 500 trades a year, at which point a streak of eight or worse is close to certain to appear.

Assume it will happen and check your sizing against it. Risk 2% per trade and eight losses cost about 15% of the account: unpleasant, survivable. Risk 10% per trade and the same streak takes 57% — you now need to double the account just to get back to flat, and you will be doing it while shaken.

Risk of ruin

Risk of ruin is the probability that your account falls below the point where you can keep trading, given your win rate, your reward-to-risk ratio and your position size. It combines edge and sizing into one number.

The result is often counterintuitive: a strategy with a genuine positive edge can still have a near-100% chance of ruin if it is sized too aggressively. Edge tells you where you end up in the long run; sizing decides whether you survive long enough to get there.

Edge first, then size

Before sizing anything, confirm you have positive expectancy: (win rate × average win) − (loss rate × average loss). If that number is negative, no position size saves you — smaller sizing only slows the bleed.

A 40% win rate is perfectly viable with a 3:1 reward-to-risk ratio (expectancy +0.6R per trade). A 70% win rate is a losing system at 0.3:1. Win rate in isolation is a vanity metric.

Practical limits

• •Risk 1–2% of the account per trade. Professionals live at the bottom of that range; the traders who blow up live above it.
• •Cap total open risk across correlated positions. Five long alt positions are one leveraged bet on Bitcoin, not five independent trades.
• •Set a monthly drawdown circuit breaker — for example, stop trading at −10% for the month. It converts an emotional spiral into a hard rule.
• •Cut size after a drawdown, not after a winning streak. Trading a smaller account with the same dollar risk quietly raises your percentage risk exactly when you can least afford it.

Judging a strategy by its drawdown

When comparing systems or backtests, look past total return to maximum drawdown, how long the recovery took, and whether you could realistically have held through it. A backtest showing 300% a year with a 70% drawdown is unusable by a human being — you would have abandoned it at the bottom, which is when its returns were being generated.