A carat is a unit of mass use to determine how much a diamond weighs. It can also relate to the size of a carat, although different diamond shapes of the same carat weight can be different sizes.

It is important to bear in mind that, while carat weight can influence the price of a diamond, no two diamonds of the same weight will worth the same. Each diamond is valued by taking into account the 4 C's: Carat, Cut, Colour and Clarity.