Carat TW stands for carat total weight. It is the combined weight of all the gemstones in a piece of jewelry.
A carat is a unit of weight used to measure gemstones. A gemstone is any precious or semi-precious stone used in jewelry, such as a diamond or a sapphire. The definition of a carat has changed through the years, but today the standard weight for one carat is 200 milligrams, or 1/5 of a gram. This system has been in place since 1913.
It is important to note that carat measures weight, not size. Sapphires, for example, are denser than diamonds, meaning that a sapphire and a diamond with the same carat weight will be different sizes. A carat is divided into units of measurement called points. There are 100 points in a carat, meaning that a half-carat stone has 50 points. Jewelers often discuss carats in terms of 1/4 carat increments.
Carat TW is only one determining factor of a gemstone’s worth. Typically, a larger stone is worth more than a collection of smaller ones, even if the total weight is equal.
Carat should not be confused with “karat.” Karat is a measurement of the purity of gold. Pure gold, being a soft metal, is rarely used in jewelry. Instead, alloys are used. A karat measurement describes how much gold versus how much alloy is in a piece of jewelry.