Why Position Sizing Matters
Two traders can use the same strategy, the same entry, and the same stop-loss — and one makes money while the other goes broke. The difference is position sizing. It determines how much you gain when you're right and how much you lose when you're wrong. Get it wrong, and even a profitable strategy will destroy your account.
Fixed Percentage Method
The most common approach: risk a fixed percentage of your account on every trade (typically 1-2%). As your account grows, your position sizes grow proportionally. As it shrinks, they shrink. This automatically scales your exposure to your current capital.
On a £10,000 account risking 1%: max risk = £100. If your stop is 25 pips, position size = £100 ÷ 25 = £4 per pip. If your stop is 50 pips, position size = £100 ÷ 50 = £2 per pip. The risk stays constant; the position size adjusts.
Volatility-Based Sizing
Some traders adjust position size based on market volatility. When volatility is high (ATR is elevated), they reduce size. When volatility is low, they increase it. The logic: a volatile market is more likely to hit your stop, so you should risk fewer pounds per pip to keep your total risk consistent.
The Average True Range (ATR) indicator is commonly used for this. A simple approach: set your stop-loss at 2× ATR, then calculate position size based on your fixed risk percentage.
Common Mistakes
The most dangerous mistake is increasing position size after losses to 'make it back.' This is the fast track to account destruction. The second mistake is inconsistency — risking 1% on some trades and 5% on others because you 'feel confident.' Confidence is not a risk management strategy. The rules should be the same on every trade.
Key Takeaways
- Position sizing determines your actual risk — more important than entry signals
- Fixed percentage method (1-2%) is the simplest and most reliable approach
- Adjust position size to the stop-loss distance, not the other way around
- Volatility-based sizing uses ATR to adapt to market conditions
- Never increase size after losses — consistency is the discipline
