Perhaps you’ve heard of karat (abbreviated K or kt), which is the most widely used measure of gold purity. Karat is measured on a scale from 0 to 24.
Thus, a piece of jewelry that has a purity of one karat consists of 1 part gold and 23 parts other metals or alloys.
Purity can also be measured in percentages and parts per thousand.
To convert karats to percentage, divide the karat number by 24 and multiply the result by 100.
For instance, to figure out the gold percentage in your 20-karat ring, divide 20 by 24, thus obtaining 0.833, or 83.3% gold content (which also translates to 833 parts per thousand).
How to Find Out the Gold Content of Your Jewelry
To see how much gold your jewelry contains, it is usually enough to look at the piece and find the stamp indicating its karat.
For instance, if you see a marking “10kt”, this means that your piece contains 10 parts gold and 14 parts other metals; this karat value also translates to 41.7% gold content.
Sometimes, you will not see purity measured in karats but rather in parts per thousand (especially common in Europe). If that’s the case, you will see a 3-digit number stamped on your jewelry.
For example, if you see the mark “583”, this means that the gold content is 583 parts per thousand. Divide that by 10 and you will get the percentage value of gold content, or 58.3%.
To find the purity of the same piece in karats, divide 583 by 1000 and multiply the result by 24 – the result is 14 karats.
Common Karat Marks on Gold Jewelry
This is how the most common parts-per-thousand purity marks correspond to standard karats:
999 = 24K
917 = 22K
833 = 20K
750 = 18K
583 = 14K
417 = 10K