Diamond Carat weight | GemTrove


Diamond Carat Weight


Diamond carat is the most widely known criteria of the four C’s. Due to their similar names, carat is often confused with the measurement for gold purity - karat. One carat is equal to 200 milligrams. This measurement can be further divided into points, which is equal to a ten-thousandth of a carat (0.02 mg). The name carat originates from the ancient Greek name for the carob tree (kerátion, literally “small horn”), which was a popular method of counterweighting metals and stones.

Despite the term having originated many thousands of years ago, there was no standard weight throughout the world, and each country or empire had its interpretation of the weight. The carat only became a standardised measurement in the early to mid 20th century, starting with the U.S. adopting the measurement in 1913. The U.K. and Europe soon followed suit, and by the 1930’s, the entire industry and every major economy had agreed to use carat as a measurement.

diamond carat weightDiamond carat and size

One common misconception about diamond carat weight is that it is directly linked to the physical size of the diamond itself. As diamonds come in a variety of shapes and cuts, the physical size of the stone is unreliable in determining the price. As an example, a 1 ct round brilliant will, on average, measure to a 6.5 mm diameter. A 1-carat marquise cut, meanwhile, will average a 10 x 5 mm size, and thus will appear bigger, despite the carat weight being identical.

This also impacts stones that have varying shallowness of their depth and pavilion, as well as elongated shapes, such as the marquise. It also addresses another misconception relating to carat and size, in that half a carat is not the half the size of one carat. This again is impacted by the dimensions of the diamond. For instance, the average diameter size for a 0.5 carat round diamond is 5 mm, while a 1-carat diamond will measure in at 6.35 mm.

Carat and Price

There is also the myth that the price of a diamond rises linearly the higher the carat weight. That is, a one-carat diamond will cost twice as much as a two 0.5 ct diamonds. In reality, the price rises exponentially. Using the previous example, a 1 ct diamond could cost more than four times the amount of two 0.5 ct diamonds. This is impacted by the desirability of the diamond cut itself, as well as the qualities of the remaining criteria that make up the 4 C’s.

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