Understanding Gold Purity: Counting in Karats
It's a common misconception when buying gold that the gold karat refers to its weight. In reality, the karat refers to gold purity (or the fineness of gold).
Gold is a precious metal used by humans to make coins, jewelry, ornaments, and art for millennia. Gold in its purest form is the most malleable metal known to man, and as such, gold is prone to losing its shape. This means that gold artisans must mix the gold with other stronger metals to create a gold alloy before crafting the alloy into its final form. The greater the volume of alloy metals used, the lower the purity of the gold—the lower the purity of the gold, the lower the karat number.
Karats refer to the number of parts gold is divided into when measuring its purity, with 24 being the total. Pure gold is 24 karat (24K). 24K gold is as pure as gold gets, although it usually has a purity of around 99.95%. 24K means that if the gold were divided into 24 parts, all parts would be gold. This logic can be applied to all other karat denominations.
- 24 parts pure gold = 24K
- 18 parts pure gold + 6 parts other metals = 18K
- 12 parts pure gold + 12 parts other metals = 12K
- 10 parts pure gold + 14 parts other metals = 10K
Anything lower than 10K cannot be considered gold in the US, and in the UK, the minimum is 9K.
The purity of gold used for most jewelry lies between 22K to 10K. Often the jewelry will have a mark that indicates its purity, and sometimes you'll find a percentage purity mark as well. To calculate the jewelry's karats from a percentage mark, divide the percentage by 100 and multiply the answer by 24. For example, a purity of 916 equals 22K (916/100=0.916*24=22).