The purity of gold is measured using the karat system. This system has been developed to measure the ratio of pure gold to other metals or alloys in a piece of gold jewellery.
Although the term “karat” sounds similar to the term “carat”, these two measurements are completely different. The karat system is used to measure gold purity, while carat is a unit of mass used to weigh diamonds and other gemstones. The measurement used to weigh gold is the troy ounce (1 troy ounce = 31.1035 grams).
Karats, marked as “k”, “K”, or “Kt”, are measured on a scale from 0 to 24, the latter being the purest form (pure gold) with no other metals mixed. The higher the karatage, the purer the gold.
The minimum gold purity for an item to be called gold varies by country. For example, in the United States, the legal minimum standard gold purity is 10k. In the United Kingdom, France and Portugal, the lowest permitted gold purity is 9k, while in Greece and Denmark, the minimum standard is 8k.