XAU/USD is the ticker for spot gold priced in US dollars, one of the most actively traded instruments on forex and CFD platforms despite gold being a metal rather than a currency. It behaves partly like a safe-haven asset (rising in times of stress or high inflation) and partly like a rate-sensitive asset (falling when real interest rates rise, since gold pays no yield).
Gold is typically quoted per troy ounce and traded with far wider point ranges than currency pairs, so position sizing needs to account for its higher dollar-per-point value.
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Work out the dollar value of one pip for any lot size and pair — the base unit for sizing every forex trade.