How to Calculate Position Sizes in Trading
Correct position sizing is the single most important aspect of risk management. Without it, you are effectively gambling. Even if your strategy has a high win rate, a few oversized trades during a losing streak can wipe out weeks of profits or result in a margin call.
The Sizing Formula
To compute your optimal position size manually, use the following formula:
Position Size (Lots) = Cash Risk Amount / (Stop Loss in Pips × Pip Value per Lot)
Key Variables Explained:
- Account Balance: The total equity in your trading account.
- Risk Percentage: The maximum percentage of your account you are willing to lose on a single trade (typically 1% to 2%).
- Stop Loss distance: The amount of space between your entry price and your invalidation point, measured in pips or points.
- Pip Value: The monetary value of one pip movement for a standard contract size. For major forex pairs on standard accounts, this is typically $10.