What Is Position Sizing?
Position sizing is the calculation that determines how large your trade should be relative to your account. It's the bridge between your risk tolerance and your actual trade — ensuring no single position can damage your account beyond acceptable limits, regardless of the outcome.
How Position Sizing Works
The standard approach uses the formula: Position Size = (Account Risk ÷ Trade Risk). If you have a $10,000 account, risk 1% per trade ($100), and your stop-loss is 5% from entry, your position size is $100 ÷ 0.05 = $2,000.
Advanced methods include:
- Fixed Fractional — Risk a constant percentage per trade (1-2% is standard)
- Kelly Criterion — Mathematically optimal sizing based on win rate and payoff ratio
- Volatility-Adjusted — Size inversely to ATR or volatility, taking smaller positions in volatile conditions
Why It Matters for Traders
Position sizing is the single most important risk management tool. A trader with a 60% win rate and poor position sizing will lose money. A trader with a 40% win rate and excellent position sizing can be profitable. It's the difference between surviving drawdowns and blowing up.