Risk of ruin and drawdown: what 200 trades can look like
Even a winning trading strategy experiences long losing streaks and deep drawdowns due to random trade sequencing. Here is how to size your risk so variance never wipes you out.
Why Positive Expectancy Does Not Prevent Drawdowns
Many traders assume that if their system has a +0.20R expectancy per trade, their account balance will climb smoothly every week. In reality, independent trades behave like a weighted coin toss: even at a 40% win rate, the probability of suffering 8 consecutive losses inside a 200-trade window exceeds 85%. If you risk 4% per trade, an 8-trade losing streakplus fee drag drops your account by nearly 30%.
Understanding Volatility Drag & Fractional Compounding
When you risk a fixed fraction f of current equity on each trade, your equity after n trades follows a geometric product. As verified in the TradeProfy Risk Lab, the analytical median ending equity multiple is:
Median Multiple ≈ exp(n × [W · ln(1 + f · netWin) + (1 − W) · ln(1 − f · netLoss)]).
Because the natural logarithm is concave, increasing f beyond a moderate threshold (typically 0.5% to 1.5% for retail traders) causes the 95th-percentile drawdown and probability of ruin to explode upward far faster than median gains.
Frequently asked questions
Can I test these formulas interactively on a live chart?
Yes. Open the TradeProfy Studio Trade Planner (/studio/trade-planner.html) to drag Entry, Stop and Target levels on a candlestick chart and see instant sizing and net R:R.
Are these calculations financial or investment advice?
No. All examples are strictly for educational risk-management and trade-cost mathematics.
Written and maintained by Mantu Kumar
Mantu builds TradeProfy’s calculation engines and checks every formula with worked examples and lists the sources and assumptions on each page. TradeProfy is an educational maths and risk-planning platform and never tells you what to buy or sell.
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