Carat to Gram Converter
Convert gemstone carats (ct) to grams (g) and grams to carats , with batch conversion and purity-weight estimations.
Carat, Gram and Milligram Converter
Use single conversions, reverse conversions, batch lists, and a quick gold purity estimator for net pure-gold weight.
Carat and gram conversions for gemstones
For gemstone mass, one metric carat is defined as exactly 0.2 gram. Multiply a carat value by 0.2 to convert it to grams, or multiply grams by five to obtain metric carats. A gemstone weighing 2.50 ct therefore has a mass of 0.50 g. This conversion is exact as a unit relationship, although a real scale reading is limited by its own precision and calibration.
Carat weight describes mass, not visible size. Two stones of the same carat weight can have different face-up dimensions because gemstone density and cut proportions differ. Likewise, a diamond and a sapphire with identical millimetre measurements will not necessarily weigh the same, even if both are shaped similarly.
Do not confuse metric carat with karat, which expresses the fineness of gold alloys. Jewellery inventory and valuation should preserve the original measurement and the scale’s reported precision rather than displaying an unjustified number of decimal places. For very small stones, weigh the stones directly whenever possible.