Gold Purity Chart

Carat	Fineness (hallmark)	Gold content	Typical use
24 carat	999	99.9%	Bullion bars, Britannia & Sovereign coins
22 carat	916	91.6%	South Asian wedding jewellery, older coins
21 carat	875	87.5%	Middle Eastern jewellery
18 carat	750	75.0%	Fine jewellery, engagement rings
14 carat	585	58.5%	Jewellery (common in the US and Europe)
9 carat	375	37.5%	Most gold jewellery sold in the UK

10 carat (417, 41.7%) is the lowest that can be sold as "gold" in the United States but is not a UK standard. Anything below 9 carat cannot legally be described as gold in the UK.

Carat vs karat vs fineness

"Carat" (ct) and "karat" (kt or k) are the same measure of gold purity — the UK spelling is "carat", the US spelling "karat". Do not confuse it with the carat used for diamond weight, which is unrelated. Fineness expresses the same thing per 1,000: 18 carat is 18/24 = 0.750 = "750". UK hallmarks use the fineness number, so a ring stamped "375" is 9 carat.

Why 24 carat gold is rarely used for jewellery

Pure gold is soft — it scratches, bends and wears quickly. Alloying it with copper, silver, palladium or zinc adds hardness and lets jewellers create colours: copper-heavy alloys give rose gold, nickel or palladium give white gold. In the UK, 9 carat dominates because it is durable and affordable; 18 carat is the standard for higher-end pieces; 22 carat is favoured in South Asian jewellery for its rich colour and closeness to pure gold.

How to read a UK hallmark

A full UK hallmark has three compulsory parts: the sponsor's mark (who submitted the item), the fineness number in a shaped shield (750, 585, 375 and so on — this is the purity), and the assay office mark (London's leopard's head, Birmingham's anchor, Sheffield's rose, Edinburgh's castle). A date letter is optional. A piece with no fineness number has not been hallmarked and its purity is unverified. Each standard also has its own per-gram price — see the 24 carat, 18 carat and 9 carat pages.

How purity sets the price

The per-gram price of any carat is the pure-gold spot price multiplied by that carat's fineness. At the same spot price, 9 carat gold is worth 37.5% of what 24 carat is worth per gram, and 18 carat is worth 75%. That is why weight alone tells you little: a heavy 9ct chain can be worth less than a light 18ct one. The live calculator applies the fineness factor for you, and the methodology page shows the formula.

Other Purities & Related Pages

1,064°C & melting by carat

Gold Density

19.32 g/cm³ & the fake-gold test

Methodology

How the price is calculated

Main Calculator

All carats in one tool

Frequently Asked Questions

9 carat is 37.5% gold, 14 carat is 58.5%, 18 carat is 75% and 22 carat is 91.6%. The rest is alloy metals such as copper, silver, zinc, nickel or palladium.

It is the fineness — the parts per 1,000 that are pure gold. 375 = 37.5% (9 carat), 585 = 58.5% (14 carat), 750 = 75% (18 carat), 916 = 91.6% (22 carat), 999 = 99.9% (24 carat).

Yes. 9 carat gold is 37.5% pure gold and is legally hallmarked and sold as gold in the UK. It is the most common gold standard for British jewellery because it is hard-wearing and more affordable than higher carats.

Only the spelling — "carat" is the UK spelling, "karat" the US one. Both mean the same: parts of pure gold out of 24. (Diamond carat, a unit of weight, is a different measure entirely.)

It is a trade-off between durability and gold content. 9 carat is the hardest-wearing and cheapest, 18 carat is a common compromise with a richer colour, and 22 or 24 carat is softest and marks most easily. Everyday wear usually points to 9ct or 18ct.

Look for three marks: the sponsor's mark (the maker or submitter), the fineness number in a shield (375, 585, 750, 916, 999 — the purity), and the assay office mark showing where it was tested (London, Birmingham, Sheffield or Edinburgh).

Pure gold is too soft — it bends, scratches and wears down quickly. Alloying it with other metals adds the hardness jewellery needs and also creates colours such as rose gold and white gold.

Gold Purity Chart