Stock Position Size Calculator
Calculate a position size from your maximum account risk and the distance between your entry and stop-loss price.
Trade risk
Define the loss before the size
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Advanced settings
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How to use
From inputs to a result you can review
- Choose long or short and enter the account size.
- Set risk as a percentage or fixed amount.
- Enter the planned entry and stop price.
- Add allocation, fees, slippage, or fractional shares when needed.
- Review the binding constraint and gap-risk scenarios.
Known limitations
What this calculation does not know
- A stop price is not a guaranteed execution price.
- Gap, liquidity, borrow, tax, and leverage risks are not fully modeled.
- The result does not determine whether the trade is suitable.
- Whole and fractional shares are rounded down to avoid exceeding the risk limit.
Educational calculation only. This is not personalized investment, trading, or tax advice.
Formula reviewed
Report an error →Method version 1.0
Calculation logic reviewed against the published methodology and automated test cases. Last updated August 5, 2026.