The term carat is used in two completely different meanings. Firstly, as a unit of weight of precious stones, but with the second it denominates the precious metal content (fineness) of alloys, mostly gold alloys. (Here the correct spelling is karat or kt.).

• As a unit of weight for gemstones applies
  • 1 carat = 0.2 g (200 mg),
  • 1 gram = 5 kt.

• For precious metals, the number of carats (or karats) indicates the amount of a precious metal in gold alloys with respect to 24 parts.

Example 18-karat gold is 75% gold (and is therefore called Gold 750).