Position Size Calculator
Use this calculator before every trade to size the position so a stop-out costs only the percentage of your account you planned to risk — the foundation of prop-firm and professional risk management.
Key takeaway: Position size equals (account balance × risk percent) divided by the dollar risk per unit (entry minus stop). Risking 1% on a $10,000 account with a $2 stop on a $50 stock means 50 shares, not a gut-feel lot size.
Calculator
Dollar risk = account balance × (risk % ÷ 100). Risk per share = |entry − stop|. Position size = dollar risk ÷ risk per share (rounded down to whole units).
Results
- Dollar risk
- $100.00
- Risk per unit
- $2.0000
- Position size
- 50 units
- Direction
- Long (stop below entry)
How this formula works
Dollar risk = account balance × (risk % ÷ 100). Risk per share = |entry − stop|. Position size = dollar risk ÷ risk per share (rounded down to whole units).
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FAQ
- What risk percent should I use per trade?
- Most discretionary traders risk 0.5–2% per trade. Prop firm challenges often require staying under a 5% daily drawdown, which usually means 0.5–1% risk per individual trade so one bad day cannot breach the rule.
- Does this work for forex lots?
- Yes. Enter entry and stop in price terms and use the pip-value calculator for forex if you size in lots. For stocks and futures, the output is shares or contracts based on the same dollar-risk formula.
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Size risk with calculators, then let Profit AI auto-sync your broker, track prop firm rules, and improve your Trader Score.