metric carat

gemology

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June 30, 2026

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The metric carat is a unit of weight used for precious gems, most notably diamonds. Before 1913, the weight of a carat varied significantly across different gem centers. It was originally based on the weight of seeds, leading to inconsistencies. After various attempts to standardize the measurement, the metric carat was adopted, equaling 0.200 grams (or 200 milligrams). This standardized unit is now used globally for weighing diamonds, rubies, sapphires, and other precious stones. The weight is often expressed in whole carats or fractions thereof, such as 1/2, 1/4, or 1/8 of a carat.12

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carat
…to standardize the carat, the metric carat, equal to 0.200 g, and the point, equal to 0.01 carat, were adopted by the United States in 1913 and subsequently by most other countries. The weights of diamond, ruby, sapphire, emerald, topaz, aquamarine, garnet, tourmaline, zircon, spinel, and sometimes opal and pearl…
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…to standardize the carat, the metric carat, equal to 0.200 g, and the point, equal to 0.01 carat, were adopted by the United States in 1913 and subsequently by most other countries. The weights of diamond, ruby, sapphire, emerald, topaz, aquamarine, garnet, tourmaline, zircon, spinel, and sometimes opal and pearl…
Read More