Karat (Gold Fineness)
Karat as a measure of gold content
Karat expresses the weight share of gold in an alloy by dividing its total weight into 24 parts. One karat is therefore 1/24 of the weight. Twenty-four karat is the reference for full gold content on the karat scale; commercial fineness is also stated with marks in thousandths.
From karat to a fineness mark
The ratio can be converted: 18 of 24 parts is 75%, corresponding to 750 fineness. Fourteen of 24 parts is mathematically about 58.3%; in Norwegian trade, 14 carat is commonly associated with 585 fineness. See the entries on 14-carat gold and 18-carat gold. Always interpret marks according to the country and rules they come from.
Gold karat and gemstone carat
For gold, karat describes fineness, not weight. For diamonds and other gemstones, a carat is a unit of mass; one metric carat equals 0.2 grams. The two measurements should not be confused when describing or assessing jewellery.
What a karat mark does not tell you
Karat alone does not identify the maker, prove authenticity or determine the alloy’s colour. Read it with any fineness, maker’s and control marks, bearing in mind that rules and spellings vary by country. Uncertain marks may require professional examination.
Sources and further reading
- Store norske leksikon: karat (gold content) – karat as the weight share of gold in an alloy.
- Store norske leksikon: fineness marks – Norwegian fineness standards and marking.
- Norway’s Precious Metals Act, section 4 – fineness expressed in thousandths.
- Gemological Institute of America: carat weight – carat as a weight unit for gemstones.
