Position Size Calculator

Position Size Calculator is a free online tool that converts the one risk decision every trader must make — how much to risk per trade — into exact order numbers: maximum shares or contracts, dollar risk, and notional value, for stocks, futures, and crypto.

Enter your account size, risk percentage, and stop-loss distance; the calculator sizes your position so the trade can never lose more than your chosen risk.

Your trade

Account balance ($)

Risk per trade (%)

Entry price ($)

Stop price ($)

Stop below entry = long · stop above entry = short

Shares already held (optional)

If you already hold some of the position

Position size

shares / contracts

Dollar risk--

Notional value--

Risk as % of account--

Stop distance--

How it works

The math is deliberately simple: decide how many dollars you are willing to lose, divide by the dollars you lose per share, and round down.

size = (account × risk%) ÷ |entry − stop|

Multiply your account balance by your risk percentage to get your risk budget in dollars.
Measure the stop distance: the absolute difference between entry and stop prices.
Divide the risk budget by the stop distance and round down — you can never buy a fraction of a share.

Because the size is rounded down, the actual dollar risk is always at or below your target — the tool reports both so you can see the difference.