Forex Position Size Calculator
Calculate lot size based on account risk, stop loss, and pip value (USD account assumption).
What the Myfxbook Position Size Calculator Helps You Do
A position size calculator solves one of the most important problems in trading: how much to trade. Instead of guessing lot size, you define your acceptable risk (for example 1% of your account), your stop loss, and the calculator tells you the correct position size.
This approach is the core of disciplined risk management. If your trade idea is wrong, the loss is controlled and predictable. If your trade is right, your upside remains open while downside stays limited.
How Position Size Is Calculated
The basic formula is straightforward:
- Risk Amount = Account Balance × Risk %
- Lot Size = Risk Amount ÷ (Stop Loss in pips × Pip Value per standard lot)
Example: If your account is $10,000 and you risk 1%, your max loss is $100. With a 25 pip stop and $10 pip value, lot size is:
Lot Size = 100 ÷ (25 × 10) = 0.40 lots.
Step-by-Step: Using This Calculator
1) Enter account balance and risk percentage
Most traders use 0.5% to 2% risk per trade. Smaller risk means smoother equity curves and better survival during drawdowns.
2) Select pair and stop loss
Stop loss should be based on market structure (technical invalidation), not on random distance. Then enter stop distance in pips.
3) Check pip value
For USD-quoted pairs like EUR/USD, pip value is generally $10 per standard lot. For USD base pairs like USD/JPY, pip value depends on current price and is auto-estimated here.
4) Calculate and round to broker lot step
Many brokers allow 0.01 lot increments. The calculator includes a conservative rounded-down lot size to keep risk from exceeding your limit.
Common Mistakes Traders Make
- Using the same lot size for every trade regardless of stop loss distance.
- Risking too much after a winning streak.
- Moving stop loss farther after entry, increasing actual risk.
- Ignoring pip value differences across pairs.
- Not rounding lot size to broker constraints.
Practical Risk Management Rules
- Risk a fixed percentage, not a fixed lot.
- Keep per-trade risk consistent with your strategy drawdown profile.
- Track expected maximum losing streak and ensure capital survives it.
- Avoid correlated exposures (multiple trades that effectively risk the same idea).
Final Thoughts
Position sizing is not a “nice to have”; it is your survival system. A mediocre strategy with strong risk control often outperforms a great strategy with poor sizing discipline. Use the calculator before every entry, make risk predictable, and let consistency compound over time.
Educational content only. Not financial advice.