Gold is traded in "units", and the minimum trade size is 1 unit which equals 1 ounce of gold. Price changes are measured in cents, eg: XAU/USD spreads are around 30, that is 30 cents, and a change in price of 205.7 is 205.7 cents. So when trading 1 unit, (which is around $1,200 nowadays) your profit or loss would be exactly that, 205.7 cents. If you trade 10 units (around $12,000), that´s a change of $20.57, etc. For a standard, $1,000 retail account with 100:1 leverage, you can trade a maximum of 83 units (83*1200=$99,600).