Just enter the weight and purity of your gold and click 'Calculate' to see how much your gold is worth. FYI: There are 31.1 grams per troy ounce, 28.3 grams per ounce, 20 pennyweights per troy ounce, and 18.2 pennyweights per ounce. Feel free to enter a different price of gold for a "what if" scenario, however, the current price of gold is already entered for you.