About the Position Size Calculator
How many shares or units to buy so a stop-loss hit risks only a set percentage of your account.
Also known as: position sizing, risk per trade, lot size calculator, stock position size, position-risk.
How to use this calculator
- Enter account size, risk per trade, entry price, stop-loss price.
- The result updates instantly as you type — press Calculate (or Enter) at any time.
- Review the breakdown shown under the main result.
- Use Copy result or Share to save the answer or send a link with your inputs.
Formula
Units = (account × risk %) ÷ |entry − stop|
Worked example
Using the values pre-filled in the calculator above:
- Account size = 25,000
- Risk per trade = 1 %
- Entry price = 50
- Stop-loss price = 47.5
the calculator returns:
- Position size: 100 shares
- Amount at risk: 250
- Position value: 5,000
- Share of account: 20%