Position sizing is the most underrated skill in trading. It doesn't matter how good your entries are if the size of your positions leads to account-ending drawdowns.
The goal of position sizing isn't to maximize returns — it's to ensure you're still in the game long enough to let your edge play out. Even a strategy with positive expectancy will lose money in the short term. Position sizing is what keeps you solvent through those inevitable cold streaks.
Method 1: Fixed Fractional (Recommended for Most Traders)
Risk a fixed percentage of your account on every trade — typically 1-2%. If your account is $10,000 and you risk 1%, that's $100 per trade, regardless of the trade setup or your recent performance.
To calculate position size: (Account Size × Risk %) / Distance to Stop = Number of Shares/Contracts
This method has the powerful property of scaling down automatically after losses (protecting your account in drawdowns) and scaling up after gains (compounding your wins).
Method 2: Fixed Dollar Amount
Risk a fixed dollar amount per trade regardless of account size. Simpler to implement, but loses the compounding benefit of fixed fractional. Good for traders who want maximum consistency and predictability.
Method 3: Volatility-Adjusted Sizing
Scale position size inversely to the volatility of the instrument. A highly volatile stock gets a smaller position than a steady, low-volatility stock with the same dollar risk. This is used by professional traders and risk managers to equalize the 'true' risk across positions.
The Universal Rule
Regardless of which method you use, define your maximum risk per trade and stick to it. Discipline around position sizing is what separates traders who are still trading in five years from those who blow up their accounts.
Track your position sizing discipline in your journal. Are you consistently within your rules? Or are you sizing up when you're confident and down when you're not? That inconsistency is itself a form of risk.
“Consistency is built through systems, not willpower. The journal is the system.”