PLAN YOUR RISK
Position Size Calculator
Estimate whole-share position size from your account balance, risk budget, entry price, and stop price.
Your result
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How to use this calculator
Adjust the inputs to your own scenario, then review the result alongside the assumptions below. The $ symbol is a currency label; the tool does not convert exchange rates.
Worked example
With a $10,000 account, 1% risk, a $100 entry, and a $98 stop, the risk budget is $100. With zero costs, 50 shares put $5,000 into the position and have a planned $100 stop loss.
The formula
Risk budget = account balance × risk %. Whole shares = floor(min(risk budget ÷ (stop distance + estimated cost per share), account balance ÷ entry price)).
What the result means
Changing position size changes the dollar risk; it does not improve the entry signal. If the cash cap applies, the planned loss may be below your chosen risk budget.
Assumptions and limitations
Sizes whole shares and caps entry notional at the account balance, with no leverage. For shorts this is only a planning cap: broker margin, borrow fees, and availability are not modeled. Costs are estimated as a percentage of entry notional and included in the risk budget; the notional cap does not reserve cash for transaction fees.
Learn more about stop-order execution risks at Investor.gov.
Common questions
Does a stop guarantee my loss?
No. A stop price is a trigger, not a guaranteed execution price. Gaps and slippage can make the actual loss larger.
Can I use fractional shares?
This tool rounds down to whole shares. Fractional-share trading and order availability depend on your broker.
Put your trading rules to the test
Explore supported daily stock rules, then review historical trades, drawdowns, and the report’s assumptions.
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Open calculator →Educational calculations, not a forecast or personalized investment advice. Your inputs are used locally for the calculation and are not submitted by this tool.
Practice stock position sizing
Choose your entry and the price that would invalidate the setup before deciding how many shares to trade. For a $10,000 account risking 1%, a $100 entry and a $98 stop allow 50 whole shares before costs. Moving the stop to $99 doubles the risk-based share count to 100, but also changes how easily ordinary price movement might reach it.
Pair this tool with the risk/reward calculator, then practice the arithmetic in Risk Manager or explore stop placement in Place Your Stop. A tighter stop is a different trade plan, not a guarantee of lower realized loss.