“Carat” is the term used to refer to the weight of a diamond (not to be confused with the term “karat” referring the purity of gold). One carat is defined as one fifth of a gram or 200 milligrams, approximately the weight of a five pound note. A carat can further be divided into “points,” where one point is equal to 0.01 carat.
While the size of a polished diamond is related to its carat weight, it is important not to confuse carat weight with size, as there are other aspects of a diamond that can affect how large an individual stone actually appears—most importantly, the cut and shape of the stone. Proportions to which an individual diamond is cut, such as table and depth percentages must be taken into account, as shallower stones can appear larger than deeper stones of the same weight. Similarly, diamond shapes can have an impact, as elongated shapes tend to maximise carat weight, making them appear larger than rounded stones of the same weight.
Furthermore, the appearance of a diamond’s size can also be affected by how the stone is set in a piece of jewellery, as well the size of the wearer’s finger (in the case of rings), therefore it is important to take all of these aspects into consideration when choosing a stone.