Summary: This article explains core money management principles for forex traders, including Kelly Criterion and fixed-fractional sizing. Practical steps to calculate position size and control maximum drawdown are provided.




Effective money management separates surviving traders from failed ones. Van Tharp, author of *Trade Your Way to Financial Freedom*, emphasized that a trading system's expectancy means nothing without proper position sizing. Many forex traders focus on entry signals but ignore how much to risk per trade. This article builds a practical money management framework for manual and EA trading.

Core Principles of Forex Money Management
The first principle is to never risk more than 1-2% of account equity on a single trade. This "1% rule" appears in nearly every professional trading guide, from Elder's *Come Into My Trading Room* to the *Market Wizards* series. Second, adjust position size based on current equity, not initial balance. Third, correlate risk with market volatility using the Average True Range (ATR).

Applying the Kelly Criterion to Forex
The Kelly Criterion calculates optimal bet size to maximize geometric growth: f* = (bp - q)/b, where b is net odds received, p is win probability, and q is loss probability. For forex, use a fractional Kelly (e.g., 0.2 × Kelly) to reduce volatility. Example: If your system has 55% win rate and 1.5 risk-reward ratio, full Kelly gives about 18% risk per trade—dangerously high. Half-Kelly drops to 9%, still aggressive for forex. Most professionals recommend 0.5-1% risk per trade, which corresponds to a tiny fraction of full Kelly.

Practical Position Sizing Steps
1. Calculate account-at-risk per trade: e.g., $10,000 account × 1% = $100 max loss.
2. Determine stop-loss in pips: 20 pips for a scalp, 50 for a swing.
3. Compute position size: $100 / (stop-loss in pips × pip value per lot). For EUR/USD, 1 standard lot = $10 per pip. So with 20-pip stop: $100 / (20 × $10) = 0.5 lots. Adjust for micro/mini lots.
4. For EA traders: code dynamic lot sizing using current equity and ATR. Avoid fixed lot sizes that ignore account growth.

Managing Maximum Drawdown
Maximum drawdown is the peak-to-trough decline in equity. A robust money management system defines a hard drawdown limit—commonly 20-30%. Once reached, trading stops, risk per trade is halved, or the strategy is reviewed. Research by John L. Kelly Jr. (1956) showed that overbetting leads to certain ruin, while underbetting only slows growth. Calculate your system's historical maximum consecutive losses, then set per-trade risk so that 5-6 consecutive losses stay within acceptable drawdown.

Reference Sources
  • Tharp, Van K. *Trade Your Way to Financial Freedom*. McGraw-Hill, 2006.

  • Kelly Jr., J.L. "A New Interpretation of Information Rate." *Bell System Technical Journal*, 1956.

  • Elder, Alexander. *Come Into My Trading Room*. Wiley, 2002.