Position sizing converts a fixed-dollar risk into a lot size. If you have a $10,000 account, risk 1% ($100) per trade, and your stop is 20 pips away, you can trade 0.5 standard lots on most majors (20 pips × $10 per pip per standard lot × 0.5 = $100). Change the stop to 10 pips and you can safely trade 1 full lot.
This is the only way to stay consistent across trades with different setups. Without sizing discipline, a single wider-stop trade can erase weeks of gains. Our position-size calculator automates this for any pair, stop distance, and account currency.