ct
metric carat
Massexact by definition
The metric carat is exactly 200 milligrams, fixed by international agreement in 1907 and adopted almost everywhere by the 1920s. Gemstones are traded by it, and the customary "points" of the trade are hundredths of a carat, so a 25 point diamond is 50 mg.
Watch out: Do not confuse it with the karat of gold purity, which is a fraction and not a mass: 18 karat means 18 parts gold in 24, and says nothing about how heavy the piece is. British usage spells both "carat", which does not help.
| 1 ct | 0.0002 kg |
Where the unit came from
From the carob seed, once believed to be uniform enough in mass to serve as a standard. It was not, and the old carats in use across Europe and Asia ranged from about 188 to 213 mg, which is why the metric value was imposed.
Solvers that use mass