Position Size Calculator
How many shares to buy so a stop loss only costs you a fixed share of your account.
Method and limitations · Report an error
Quick answer
Size a position from a fixed amount of risk
This position-size calculator converts the selected account-risk percentage into a cash risk limit. It divides that amount by the distance between entry and stop loss to estimate the number of whole shares.
Use this calculator when
- Keeping the same risk limit across differently priced shares
- Testing how a wider stop changes the affordable position
- Estimating position value before placing an order
How to read the result
The calculated loss assumes execution at the exact stop price. Gaps, slippage and fees can make the realised loss larger, while broker rules or available cash may reduce the position that can actually be opened.
- Place entry and stop at different prices
- Treat the result as a sizing estimate rather than a loss guarantee
Method
How it works
Choose how much of the account may be lost if the stop is reached. The calculator converts that percentage into a cash risk amount and divides it by the absolute distance between entry and stop.
The share count is rounded down to a whole number, which keeps the calculated position within the selected risk amount before fees and slippage.
Common questions
Frequently asked questions
Why is the share count rounded down?
Rounding down avoids exceeding the selected cash risk because fractional shares may not be available.
Can the stop be above the entry price?
Yes. The calculation uses the absolute difference between the two prices.
Does this include slippage or commissions?
No. Those costs can increase the actual loss beyond the displayed risk amount.
Not financial advice. This calculator is for general informational purposes only. Check figures independently before making financial decisions.