Carat Weight is probably one of the most important characteristics when considering consumer preference. It is also the biggest factor in determining a stones rarity. When diamond rough is cut and polished into finished diamonds, as much as 2/3rd of the total carat weight is lost. Because larger gem quality rough is found less frequently than smaller rough, a 2 carat diamond will be about 3 times more valuable than a comparable quality 1 carat.
Keep in mind, carat weight and size are not directly proportional. A diamond will increase in weight faster than it increases in actual size (diameter). For example, a 2 carat diamond will not be twice the size of a 1 carat diamond. A 1 carat diamond is approximately 6.5mm in width, while a 2 carat diamond is only 8.2mm in width. This is less than a 30% increase in millimeter size.
Click the image on the right to view the Diamond Size Guide