Gold Purity
The proportion of pure gold in a piece, expressed as a karat number or as fineness such as 916 or 750.
Gold purity is the single most important fact about a piece of gold jewellery: how much of it is actually gold rather than the other metals mixed in for strength and colour. It is expressed two ways that mean the same thing, as karat out of 24, or as fineness in parts per thousand, so 22K and 916 both describe metal that is 91.6 percent gold. Purity decides the colour, the durability, what hallmark the piece carries, and, together with weight and the gold rate, exactly what the metal is worth.
Two ways to state the same thing
Karat measures purity in twenty fourths, so 24K is pure gold and 18K is 18 parts in 24. Fineness measures the same purity in parts per thousand, so 750 means 750 parts gold out of 1000. Convert between them by dividing the karat by 24 and multiplying by 1000: 18 divided by 24 is 0.75, times 1000 is 750.
The common grades line up as: 24K is 999 fineness, 22K is 916, 18K is 750, and 14K is 585. Hallmarks may show either the karat, the fineness or both, but they are describing one property, the share of pure gold in the alloy.
- 24K equals 999 fineness, 99.9 percent gold.
- 22K equals 916 fineness, 91.6 percent gold.
- 18K equals 750 fineness, 75 percent gold.
- 14K equals 585 fineness, about 58.5 percent gold.
What purity affects
Purity shapes three things a buyer notices. Colour deepens as purity rises, so 22K looks richer than 18K. Durability falls as purity rises, because pure gold is soft, which is why stone set pieces favour 18K or 14K. And hallmarking is tied to purity, since the mark certifies exactly which grade the piece is.
It also underpins the price. The purity fraction, 0.916 for 22K or 0.75 for 18K, converts a piece's weight into its pure gold content. That content, multiplied by the current gold rate, gives the metal value that sits at the base of the final price before stones, making charges and taxes.
Checking purity is genuine
A buyer's assurance that the stated purity is real comes from hallmarking. In India the BIS hallmark certifies the grade with a logo, a fineness number and a unique HUID after the metal is assayed by an authorised centre, so the stamp is not just the seller's word.
For a jewellery business, storing purity as structured data against every product, rather than as free text, means the right purity fraction always feeds the price calculation. When the gold rate changes, each piece reprices correctly according to its own purity.
- Gold purity is the share of pure gold in a piece.
- It is shown as karat out of 24 or fineness in parts per thousand.
- 22K is 916, 18K is 750, 14K is 585, 24K is 999.
- Purity sets colour, durability and hallmark grade.
- The purity fraction converts weight into metal value.
Gold Purity, in short.
How do I convert karat to fineness?
Divide the karat by 24 and multiply by 1000. 18K is 18 divided by 24, which is 0.75, times 1000 gives 750. 22K works out to 916 the same way.
Which gold purity is best?
It depends on use. 22K gives richer colour and more gold for traditional pieces, while 18K and 14K are harder and better for stone settings and daily wear. There is no single best, only the right fit for the piece.
How does purity affect the price?
Higher purity means more pure gold per gram, so a higher metal value for the same weight. The purity fraction, such as 0.916 for 22K, multiplies weight and the gold rate to give that metal value.
How can I be sure of a piece's purity?
Look for the hallmark. In India the BIS hallmark certifies the purity grade after official assaying, showing the BIS logo, a fineness number and a unique HUID code.
Related terms
See gold purity inside a real jewellery system.
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