Position sizing is the most underrated skill in trading. Two traders can use the exact same entry and exit signals and produce completely different results — one profitable and one bankrupt — based solely on how much capital they allocate to each trade. In Indian markets, where F&O leverage can amplify both gains and losses 5–10x, getting position sizing right is the difference between longevity and blowup.
The 1% rule states that no single trade should risk more than 1% of total trading capital. If your capital is ₹10 lakhs, the maximum loss on any single trade is ₹10,000. This means your position size is determined by your stop-loss distance, not by how much you want to make.
Position Size = (Capital × Risk%) ÷ Stop-Loss Amount per Share
Example: ₹10L capital, 1% risk = ₹10,000 max loss
Stock at ₹500, stop at ₹480 (₹20 risk per share)
Position Size = ₹10,000 ÷ ₹20 = 500 shares
A fixed 1% rule treats all setups equally. Volatility-adjusted sizing is more sophisticated — it reduces position size when the market is volatile (VIX above 18) and increases it when conditions are calm. The logic: higher volatility means wider price swings, which requires either a wider stop (more risk) or a smaller position (same risk, narrower stop relative to noise). Always check India VIX before sizing positions.
| India VIX Level | Position Size Adjustment | Rationale |
|---|---|---|
| Below 13 | 100% normal size | Low volatility — stops less likely to be hit by noise |
| 13–18 | 75–100% normal size | Moderate volatility — standard sizing appropriate |
| 18–25 | 50–75% normal size | Elevated volatility — reduce size, widen stops |
| Above 25 | 25–50% normal size | High volatility — preserve capital; large swings likely |
Portfolio heat is the total percentage of capital at risk across all open positions simultaneously. Even if each individual trade risks 1%, having 15 open positions means 15% portfolio heat — a correlated market move can trigger all stops simultaneously. For Indian equity traders, limiting total portfolio heat to 5–8% across all positions is a practical guideline. In F&O, given higher leverage, limiting heat to 3–5% is more appropriate.
The Kelly Criterion calculates the theoretically optimal fraction of capital to bet per trade when you know your win rate and average win/loss ratio:
Kelly % = Win Rate − [(1 − Win Rate) ÷ (Avg Win ÷ Avg Loss)]
Example: 55% win rate, 1.5:1 win/loss → Kelly = 0.55 − (0.45 ÷ 1.5) = 0.55 − 0.30 = 25%
Full Kelly sizing is extremely aggressive and produces large drawdowns. Most professional traders use Half-Kelly or Quarter-Kelly in practice. The formula's real value is in revealing when your edge is insufficient: a Kelly percentage below 5% indicates your edge is too thin to size up significantly regardless of your conviction.
The most common error is averaging down — adding to a losing position to reduce the average cost. This directly violates position sizing discipline by increasing exposure as evidence mounts against your thesis. In Indian markets, where stocks can fall 30–50% on a single event (SEBI action, promoter fraud, earnings miss), averaging down on F&O positions has been responsible for the most catastrophic retail trading losses.
Real-time India VIX, FII flows, and market breadth to calibrate your position sizing every session.
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