CTW stands for carat total weight. It is used to evaluate jewelry that contains multiple diamonds throughout the piece. Carat total weight is one of the factors used to determine the value of diamond jewelry.
A carat is equal to 200 milligrams. Though the weight is the same, the size of a carat may change depending on the type of gem being measured. The reason for this difference is that gems have different densities.
The shape and cut of a diamond can make it difficult to effectively judge the carat weight of the stone. For this reason, diamond weight estimators take these factors into account to provide consumers with information about the value of their piece.