Karat Purity of Gold

Gold

Gold is mixed with alloys, metals added to strengthen the gold to create more durable jewelry, particularly in gold rings and gold bracelets. There is very little 24 karat gold jewelry sold in the world. 24 Karat gold is soft and not very durable for jewelry. Mixing other metals to create a gold alloy gives strength and hardness to gold jewelry. This means gold jewelry wears better, is less scratch resistant and will not be damaged or distort as readily as 24 Karat gold jewelry.

So, gold measurements can be a bit confusing. The weight of gold is measured in troy ounces or Tola (Bhori) or grams, but its purity, or fineness is measured in a few different ways: "parts fine," "% gold", and karats.

Gold Jewelry

“Karat” is also spelled “Carat” outside the United States but should not be confused with the unit used to measure the weight of gems or stones, also called carat.

A major point of confusion is between "carat," which is a measure of weight for precious stones or gems, and "karat", which is a measure of purity or fineness for gold.

Karats in Gold Jewelry refer to the amount of gold that is present in the jewelry piece. Europe describes the purity of gold jewelry in ‘fineness’, which is the gold content expressed in parts per thousand.

Karat purity of gold alloy is measured as 24 times of the pure gold by the gold alloy,

i. e.  Karat (K) = 24 X (mass of pure gold / total mass of gold alloy)

Example: 18 Karat Gold, where 18 of the 24 parts are gold and 6 parts are one or more additional metals. 

Gold Alloy (24 Parts)		Karats Parts	Percent (%)	Fineness (per thousand)
Pure Gold	Other metals
24	-	24	99.99	999
23	1	23	95.83	958
22	2	22	91.67	916
21	3	21	87.50	875
20	4	20	83.33	833
19	5	19	79.17	791
18	6	18	75.00	750
17	7	17	70.83	708
16	8	16	66.67	666
15	9	15	62.50	625
14	10	14	58.33	583
13	11	13	54.17	541
12	12	12	50.00	500
11	13	11	45.83	458
10	24	10	41.67	416

Gold Rings

There is X-ray fluorescence instrumentation available to test the karat measurement of precious metals and finished jewelry. These machines allow a karat gold measurement without damaging fine jewelry. Some can also accurately determine the element composition of gold jewelry including gold, platinum, silver, paladium, rhodium and related alloys.