Forex Lot Size Calculator

Lot size = (account balance × risk %) ÷ (stop-loss pips × pip value). Below the calculator does the math live — change any input, see the answer instantly. Built for traders running prop-firm risk plans where a single oversized trade can blow the daily DD limit.

• Standard lot = 100,000 units of base currency
• Mini lot = 0.10 (10,000 units)
• Micro lot = 0.01 (1,000 units)
• Most prop firms cap risk per trade at 1-2% of account balance

Why Position Sizing Matters for Prop Firms

Prop firms enforce hard daily and overall drawdown limits. FTMO's daily DD is 5%, FundedNext's is 5%, TopStep's is dynamic. One oversized trade can hit the daily DD limit and end your challenge instantly — even if the broader strategy was profitable. The fix is mechanical: compute your lot size BEFORE every trade based on your stop-loss distance and a fixed risk percentage of account balance.

Recommended Risk Per Trade by Strategy

• Scalper (10-20 pip stops): 0.5-0.75% per trade
• Day trader (30-50 pip stops): 1-1.5% per trade
• Swing trader (100-200 pip stops): 1-2% per trade
• News trader: 0.25-0.5% (volatility multiplies the loss)

Related Tools

• Prop Firm Drawdown Calculator — what's your daily DD ceiling?
• FTMO Fee Calculator — entry cost by account size
• All prop firm reviews