Carat is a unit of weight and is usually used as a unit of measurement for precious stones. 1 carat is 200 mg. Carat originated from carob trees, and the weight of each nut is accurate and consistent, so it is used as a weight to weigh valuable and subtle objects. Hello, it's my pleasure to serve you and give you the following answer: In the jewelry industry, the unit of measurement for gems is carats. 1 carat equals 0. 2 grams, which is 200 milligrams. 1。 Carat: The most commonly used unit of measurement for gem weight. 1 carat equals 0. 2 grams. 2。 Pound: 1 pound equals 453. 59 carats, commonly used in jewelry industry. 3。 Oz: 1 oz equals 28. 35 carats, commonly used in jewelry industry.