The price per ounce for all types of gold, including 18-karat gold, changes a number of times throughout the day. Eighteen-karat gold prices typically vary by as much as $10 per ounce throughout the course of a day.
The value of the U.S. dollar is a good indication of current gold prices, though global economic and political situations also play a role. The price per ounce of 18-karat gold is indirectly related to the purchasing power of the U.S. dollar. As the value of the dollar increases, the price of gold decreases, and vice versa. The U.S. dollar experiences numerous small changes in value on an hourly basis, and gold prices usually reflect these changes.