Position Sizing: The Most Ignored Skill in Trading

## Why Position Sizing Matters More Than Your Strategy Two traders can use identical entry/exit rules and have completely different results — purely because of how they size their positions. Trader A: Sizes every trade at 10% of portfolio Trader B: Sizes based on volatility and risk After 20 trades with a 60% win rate and 1.5:1 R:R: - Trader A: +18% but with 34% maximum drawdown - Trader B: +22% but with only 12% maximum drawdown Same strategy. Wildly different risk-adjusted outcomes. ## The Three Main Position Sizing Methods ### 1. Fixed Dollar Risk Risk a fixed rupee amount per trade regardless of market conditions. **Example:** Risk ₹5,000 per trade If your stop is 2% below entry on a stock at ₹500: Stop = ₹490, Risk per share = ₹10 Shares to buy = ₹5,000 / ₹10 = 500 shares Position value = 500 × ₹500 = ₹2,50,000 Simple, consistent, easy to track. ### 2. Fixed Fractional (% of Capital) Risk a fixed percentage of your current portfolio on each trade. **Standard rule:** Risk 1–2% of capital per trade ₹10 lakh portfolio → risk 1% → max ₹10,000 per trade This method automatically reduces size after losses (protecting capital) and increases size after wins (compounding gains). It's the most recommended method for algorithmic traders. ### 3. Kelly Criterion The mathematically optimal bet size for maximizing long-run wealth. **Kelly % = Win Rate − (Loss Rate / Win:Loss Ratio)** If your strategy wins 60% of the time with 1.5:1 R:R: Kelly % = 0.60 − (0.40 / 1.5) = 0.60 − 0.267 = **33.3%** 33% per trade is extremely aggressive — most practitioners use **Half Kelly (16%)** or **Quarter Kelly (8%)** to reduce volatility. For most retail traders: **use 25–50% of Kelly at most.** ## Volatility-Based Sizing (ATR Method) Position size based on the instrument's recent volatility. 1. Calculate 14-day ATR (Average True Range) 2. Set risk = 1% of portfolio 3. Shares = (1% × Capital) / (2 × ATR) **Example:** - Capital: ₹10 lakh - Stock price: ₹1,000, ATR(14) = ₹25 - Risk budget: ₹10,000 - Shares = ₹10,000 / (2 × ₹25) = 200 shares - Position = 200 × ₹1,000 = ₹2 lakh (20% of portfolio) This automatically sizes smaller in volatile markets and larger in calm ones. ## For Options Traders Options have non-linear risk. Never size options positions by notional value. **Rule:** Risk only what you pay in premium (for buyers) **For option sellers:** Size by max loss of the spread, not by premium collected If you sell an Iron Condor with max loss of ₹15,000 per lot: At 2% risk on ₹10 lakh = ₹20,000 max Max lots = 20,000 / 15,000 = 1 lot (round down conservatively) ## Correlation-Adjusted Sizing If you trade correlated instruments (e.g., NIFTY and BANKNIFTY), their positions are not independent. During a market crash, both will lose simultaneously. Treat correlated positions as a single position for sizing purposes — reduce individual sizes by 50% when holding both. ## Practical Rules 1. **Never risk more than 2% on a single trade** 2. **Never risk more than 6% total on correlated positions** 3. **Reduce size by 50% after 3 consecutive losses** 4. **Return to normal size only after 3 consecutive winners** 5. **Never add to a losing position** (averaging down is a path to ruin) ## Conclusion Position sizing is the difference between surviving long enough to find your edge and blowing up before you get there. Master this before you worry about your entries.