Position Size Calculator

Turn a maximum loss per trade (percent or dollars) and a stop price into how many units to buy or sell, plus how much notional that puts on the table.

Position sizing links your risk budget to where you admit you are wrong (the stop). Wider stops mean fewer units for the same dollar risk, tighter stops allow more units. This calculator does not tell you where to put the stop, it only sizes from numbers you supply.

Long and short modes use the same idea: risk per unit is the distance from entry to stop in the direction that hurts your position. Notional at entry helps you see total exposure, not just risk.

Risk per trade
Position size (units)20
Notional at entry2,000
Risk per unit (stop distance)5
Dollar risk (if stop hits)100
Notional % of account20%

Assumes a single stop price and no fees or slippage. Round down in practice if your broker requires whole shares.

Frequently Asked Questions

Percent risk scales with account size: a 1% rule keeps each loss small relative to equity. A fixed dollar amount is simpler mentally but does not adjust as your balance changes. Many traders use a percent for consistency.
Risk per unit is how far price can move against you before you exit at the stop. The calculator divides your chosen dollar risk by that distance to get how many shares or units fit that risk budget.
The tool shows a mathematical size from your inputs. It does not round to whole shares or subtract commissions. Apply your broker’s rules and costs when you actually place the order.

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