Diamond carat weight is the measurement of how much a diamond weighs and thus reflecting its apparent size. The carat, the standard unit of weight for diamonds, takes its name from the carob seed. Because these small seeds had a fairly uniform weight, early gem traders used them as counterweights in their balance scales.
Today diamonds and other gemstones are weighed in metric carats: one carat is equal to 0.2 grams or 200 milligrams, about the same weight as a paperclip. (Don’t confuse carat with karat, as in “18K gold,” which refers to gold purity.)
Because even a fraction of a carat can make a considerable difference in cost, precision is crucial. Therefore, just as a dollar is divided into 100 pennies, a carat is divided into 100 points. For example, a 50-point diamond weighs 0.50 carats and may be described in the diamond industry as a “50 pointer”. Diamond weights greater than one carat are expressed in carats and decimals. For example, a 1.08 carat diamond would be described as “one point oh eight carats,” or “one oh eight.”