Because of the high value of diamonds, the unit of valuation is generally carats, 1 carat =0.2 grams. For smaller diamonds, it is a few tenths of a carat. For convenience, the weight is generally measured in units. 1 carat = 100 integral. For example, a 30-cent diamond ring weighs 0.3 carat, or 0.06 gram. Diamonds smaller than 1 are called centimeters, and10cm = 1 cm. Very, very small. Diamond rings are generally recommended to buy more than 30 cents, and the value composition of diamonds includes size, fineness grade, clarity grade and cut. That is, the 4C of a diamond.