The weight of a diamond is expressed in carat, this is the weight of measure that the jewellery industry uses to weigh diamonds.
The word carat originated from the carob tree. The tiny seeds of this tree are well known for their uniformity and consistent weight. Traditionally diamonds and other precious stones ( rubies, saphires and emeralds ) were weighed against these seeds until the system was standardized, and one carat was fixed at 0.20 gram.
One carat is divided into 100 points. A diamond solitaire or ring weighing one quarter of a carat can also be described as weighing 25 points or 0.25 carat. Points are generally not used to describe weights over one carat.
The chart below outlines various diamond weight sizes and the corresponding millimeter size. The dimensions of the diamond should tell you how large the diamond will appear. This chart is not scaled and should only be used as reference.
Since a carat is a unit of measure and not a size, two diamonds of the same weight may appear to be of a different size depending on how the diamond is cut. Some diamonds will have extra weight on the bottom part of the diamond, the pavillon, and therefore will appear smaller visually.
More the weight of a diamond is high for a given quality more the price per carat is higher. For instance a three-carat ( 3.00 ct) diamond of a specific quality is always more expensive than several diamonds of the same quality which added up represent three carats in total weight.
Do not be mistaken by the belief that the larger the carat weight, the more valuable the diamond. While this can be true, it is not necessarily so. Keep in mind that a diamond’s colour, clarity and the other 4 criteria ( symmetry, proportions, finish and degree of fluorescence ) are major factors that influence the value of a diamond.
For that reason, it is important for every potential diamond buyer to understand the importance of each of these characteristics and the impact it can have on the value of a diamond, when considering the purchase of a diamond. These characteristics are more commonly known as the 4C’s : Cut - Colour - Clarity - Carat.
Remember that choosing a diamond jewel is not an exact science and a diamond buyer should decide what characteristics are more important to them and set some parameters to help choose the most suitable diamond.