Position Size Calculator
Position sizing is the risk lever you fully control before a trade. The discipline behind almost every risk framework is simple: never lose more than a fixed, small percentage of your account on a single trade. This calculator turns that rule into a concrete number of shares or units, so a stop-out costs exactly what you decided — no more.
- • Capital at risk = account size × risk %. It's the most you'll lose if the stop is hit.
- • Risk per unit = the distance from entry to stop, |entry − stop|.
- • Position size = capital at risk ÷ risk per unit, rounded down so you never exceed your limit.
Worked example: a $10,000 account risking 1% puts $100 on the line. With a $100 entry and a $95 stop, you're risking $5 per share, so you buy $100 ÷ $5 = 20 shares.
Assumes the stop fills at your price — gaps and slippage can make a real loss larger — and ignores fees. Educational tool, not advice.
A calculator shows what a rule should do on paper. Whether a strategy actually beats simply buying and holding — costs on, losses shown, no hindsight — is a different question, and the only one that pays. Test one on real data, free, no sign-up.