Diamonds and other gemstones are weighed in metric carats. It is derived from the carob seed, which is remarkably consistent in weight and shape making them the favored scale balances in ancient times. The scale was standardized in the early 1900’s when it was determined that one carat was 0.2 grams or 1/142 of an ounce. Just as a dollar is divided into 100 pennies, a carat is equal to 100 points. A half carat diamond is equal to 50 points. It is possible that two diamonds could weigh the same, however their values can vary based on the other cut, clarity and color. A majority of the diamonds used in fine jewelry weigh one carat or less.
You’ve probably heard of 18 Karat gold. The term “Karat” is used to describe the purity of gold whereas “Carat” is the standard unit of weight for diamonds and other gemstones. Even a fraction of a carat can make a considerable difference in cost making precision crucial. Weight is often measured to the hundred thousandths of a carat in the diamond industry and rounded to a hundredth of a carat. Diamonds that weigh more than one carat are expressed in carats and decimals. A diamond stone weighing 1.08 ct. would be described as “one point oh eight carats.