Understanding Diamond Carats

The carat of a diamond refers to its weight, rather than its size. The term carat evolved from different languages’ word for carob. The carob seeds themselves are inedible, but they were observed to have a very uniform size and weight, which made them very useful for traders.

The seeds were used to balance a scale when weighing precious gemstones, where the tiniest change in weight makes a difference. A higher number of seeds indicated a heavier and therefore more valuable stone.

Different countries had slightly different values for what number of seeds was equivalent to what value of gems, but the use of the seeds was consistent throughout the Middle East and Europe.  In areas of the world where carob was not as popular, grains of wheat or rice were used in similar ways to discern the weight of diamonds.

In 1907, the Fourth General Conference on Weights and Measures adopted the Metric Carat as the official measurement for gemstone weights; today it is universally accepted. One metric carat is one fifth of a gram, which is 0.2 grams – about the weight of a raisin!