The gold/silver ratio is the amount of silver it takes to buy one (1) troy ounce of gold. To find the gold/silver ratio, simply take the spot price of gold and divide it by the spot price of silver.
Gold Spot / Silver Spot = Gold/Silver Ratio
Hystorically, the romans price ratio was set to 12 to 1 and in 1792 the United States set it to 15:1. In recent years the ratio is closer to 66:1.