Position Size Risk Calculator

About this calculator

Position sizing by risk keeps every trade's worst-case loss to a fixed, chosen percentage of the trading account, regardless of how far away the stop-loss sits. The formula is: position size (units) = (account size × risk percentage) ÷ (entry price − stop-loss price), so a wider stop automatically results in a smaller position and a tighter stop allows a larger one, keeping the dollar risk constant across trades.

Traders use this calculation because sizing positions by a fixed number of shares or a fixed dollar amount, without regard to stop distance, means volatile setups with wide stops can silently blow past a trader's intended risk tolerance. Standardizing risk per trade — commonly 1% or 2% of account equity — is one of the most widely cited risk-management practices for avoiding account-ending losses from any single bad trade.

This calculator takes your account size, risk percentage, entry price and stop-loss price, and returns exactly how many units to buy so a stop-out costs only the risk you chose.