# Carats to Grains (ct to gr) Source: https://www.unitconvertercalculator.com/weight/carats-to-grains/ **1 ct = 3.0864716705883 gr** One carat equals approximately 3.0865 grains. The grain is one of the oldest and most persistent weight units, identical across the troy, avoirdupois, and apothecary systems at exactly 64.79891 milligrams. Since a carat is 200 milligrams, each carat contains just over three grains, making this a practical conversion for jewelers and pharmacists working across historical measurement systems. ## Formula Apply the conversion factor ## Conversion Table | Carats (ct) | Grains (gr) | |---|---| | 0.25 ct | 0.77161791764707 gr | | 0.5 ct | 1.5432358352941 gr | | 1 ct | 3.0864716705883 gr | | 2 ct | 6.1729433411766 gr | | 3 ct | 9.2594150117649 gr | | 5 ct | 15.432358352941 gr | | 10 ct | 30.864716705883 gr | | 25 ct | 77.161791764707 gr | | 50 ct | 154.32358352941 gr | | 100 ct | 308.64716705883 gr | | 250 ct | 771.61791764707 gr | | 500 ct | 1543.2358352941 gr | | 1000 ct | 3086.4716705883 gr | | 5000 ct | 15432.358352941 gr | ## Units ### Carat (ct) A carat is a unit of mass equal to exactly 200 milligrams (0.2 grams), used for measuring gemstones and pearls. Adopted internationally in 1907 by the Fourth General Conference on Weights and Measures. ### Grain (gr) A grain is a unit of mass equal to exactly 64.79891 milligrams. It is the same in the avoirdupois, troy, and apothecaries' systems, derived from the 1959 international agreement defining the pound as exactly 0.45359237 kilograms. ## Background Grains remain actively used in ammunition (bullet weights are specified in grains), archery (arrow spine and point weight), and some pharmaceutical dosages. A typical aspirin tablet weighs about 5 grains (325 mg), which is roughly 1.625 carats. Diamond traders rarely think in grains, but antique jewelry documentation sometimes recorded gemstone weights this way, requiring conversion for modern appraisals. ## Good to Know The grain is remarkable for being the one unit that survived unchanged across all three English weight systems. When Parliament standardized weights and measures, the grain served as the common anchor: 7,000 grains made one avoirdupois pound, 5,760 grains made one troy pound. This shared foundation is why the grain could serve as a Rosetta Stone for converting between the otherwise incompatible systems. ## FAQ ### How many grains are in one carat? One carat equals approximately 3.0865 grains. This is derived from 1 carat being exactly 200 milligrams and 1 grain being approximately 64.799 milligrams. ### Is the grain the same in all weight systems? Yes. The grain is uniquely consistent: 1 grain equals exactly 64.79891 milligrams in the troy, avoirdupois, and apothecary systems. It is the only unit shared identically across all three traditional English weight systems. ### Where are grains still used today? Grains are actively used in ammunition manufacturing (bullet and powder charge weights), archery (arrow component weights), and some pharmaceutical compounding. They also appear in water hardness measurements (grains per gallon). ## Non-Frequently Asked Questions ### Is the grain named after an actual grain of wheat? Yes. The grain was originally defined as the weight of a single grain of barley or wheat, taken from the middle of the ear. Of course, individual grains vary considerably in weight, which is why medieval measurement was more of an art than a science. The modern grain is standardized and no longer depends on the agricultural output of any particular field. ### If I loaded a rifle cartridge with diamonds instead of powder, how many carats per grain? A typical rifle powder charge is 40 to 50 grains. At 3.0865 grains per carat, that would be roughly 13 to 16 carats of diamond powder - about 2.6 to 3.2 grams. You would destroy several thousand dollars worth of diamonds and produce no useful ballistic effect. Please do not attempt this. ### How many grains of rice equal one carat of diamond? The grain unit and a grain of rice are very different things. A single grain of uncooked rice weighs about 25 to 30 milligrams, meaning one carat (200 mg) weighs as much as roughly 7 to 8 grains of rice. 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