Position sizing, the actual math
By the XAUUSDLiveChart Research Desk · 5 min read
Position sizing is the only part of trading where you control the outcome completely, and it is four lines of arithmetic. Decide the fraction of the account one trade may lose, measure the stop distance the chart demands, and the lot size falls out. Done every time, every loss costs the same and no single trade can matter too much. Skipped, the best strategy in the world remains one bad evening from ruin.
The formula
Risk amount = account balance x risk percent. Lot size = risk amount / (stop distance in dollars x contract ounces). With a standard XAUUSD lot of 100 ounces, a one-dollar move is 100 dollars per lot. That is the whole engine.
A worked example
Account 5,000; risk one percent = 50. The setup needs a 4.00 stop. Per-lot cost of that stop: 4 x 100 = 400. Lot size = 50 / 400 = 0.125, so 0.12 rounded down. The trade now loses about 48 if wrong, forever, regardless of how confident it felt.
Stop first, size second
The order of operations is the discipline: the chart sets the stop where the idea is invalid, then the stop sets the size. Traders who fix the size first end up placing stops where the mathematics is comfortable instead of where the idea dies, which is how correct analysis still loses money.
The classic errors
Rounding lot size up instead of down; risking the same lots on a 3-dollar and a 9-dollar stop and calling it consistent; widening a stop mid-trade without cutting size, which silently multiplies risk; and sizing from margin available rather than from risk, covered further in margin and leverage. Each error breaks the one guarantee sizing exists to provide.
FAQ
What risk percent should I use?
Common professional practice sits at or under one to two percent per trade. The exact number matters less than applying it identically to every trade.
How much is one XAUUSD pip or dollar worth?
On a standard 100-ounce lot, each 1.00 move in the gold price is 100 in account currency; a 0.10 move is 10. Scale linearly for mini and micro lots.
Should winners change my size?
Recalculate from current balance on a schedule, weekly or monthly. Ratcheting size trade-by-trade after wins reintroduces the streak risk sizing exists to remove.
Ready to see it live? Open the XAUUSD live chart and try these ideas on real price.