The carat is the unit of measurement used to evaluate the weight of gemstones, including diamonds. The weight of diamonds is one of the determining factors in their price, along with the cut, color, and clarity. Weight is measured to the hundredth of a carat, and a carat is divided into 100 points. One point is equivalent to one-hundredth of a carat (0.002 grams).
The metric carat, adopted in 1907, is equal to 0.20 grams. The word “carat” is believed to have originated from “kuara,” the name of the seed of an African tree called the carob tree.
In antiquity and until 1907, these seeds were used as counterweights on scales. While these seeds were known for their regular size and weight, it’s easy to imagine that the evaluation was still somewhat approximate.
The price of a diamond changes with its weight and is set at certain thresholds. There is a price difference between a 0.89-carat diamond and a 0.9-carat diamond because they fall within different weight thresholds. When it comes to larger stones, the price is not directly proportional to their weight. For example, three 2-carat stones do not have the same value as one 6-carat stone.
The specific dimensions and regularity of a diamond are used to estimate a stone’s weight. For a round diamond, the formula is depth x radius² x 0.0245.
This table provides the approximate diameter of a round diamond based on the chosen carat weight. The diameter remains approximate because it depends on how the diamond is cut. Nevertheless, it will give you an idea of how it may appear on the hand.