Karat versus carat
Karat (k or kt) measures the purity of gold. Carat (ct) measures the weight of gemstones, where one carat equals 0.2 grams. In British English both are often spelled 'carat', which is why you will see '24 carat gold' in the UK, India and the Gulf, and '24 karat gold' in the United States. They mean exactly the same thing when used for gold.
The karat system divides an item into 24 equal parts. The karat number tells you how many of those parts are pure gold; the rest is an alloy of other metals such as silver, copper, zinc, nickel or palladium. Those alloy metals make gold harder, change its colour and lower its cost.
Karat to fineness conversion table
Fineness is the same information expressed in parts per thousand, which is what most modern hallmarks show. These are the standard grades and the mark you are most likely to see:
- 24k = 99.9% gold, stamped 999 or 9999 for 'four nines' bullion.
- 22k = 91.6% gold, stamped 916. Standard for jewelry in India, Pakistan and the Gulf, and for gold Sovereigns.
- 21k = 87.5% gold, stamped 875. Very common in Saudi Arabia, Egypt and much of the Middle East.
- 18k = 75% gold, stamped 750. The European fine-jewelry standard.
- 14k = 58.5% gold, stamped 585. The most popular grade in the United States and Eastern Europe.
- 10k = 41.7% gold, stamped 417. The legal minimum to be sold as 'gold' in the US.
- 9k = 37.5% gold, stamped 375. The lowest common grade in the UK, Ireland and Australia.
Why hallmarks use 585 instead of 583
Mathematically, 14/24 is 0.5833. Many countries nevertheless stamp 585 because the hallmark represents a minimum guaranteed fineness, and manufacturers add a small safety margin so that every item tests at or above the legal standard. Older Soviet and Eastern European jewelry is often marked 583, and some Indian and Gulf jewelry is marked 916 for 22k even though 22/24 is 0.9167. For pricing, AurumValue uses the stamped standard because that is how buyers and assay offices treat the metal.
How purity changes the price per gram
Because karat gold is just pure gold diluted with other metals, its value scales almost exactly with its purity. If one gram of pure gold costs 100 units of your currency, a gram of 22k is worth about 91.6, a gram of 18k about 75 and a gram of 14k about 58.5. You can see the live figures side by side on the gold price per gram by karat page, or open a single grade such as 18k gold or 24k gold.
The alloy metals add almost nothing. Silver and copper are worth a tiny fraction of gold, and buyers do not pay for them. Palladium in some white gold is the exception, but even then refiners rarely pay for it on small lots.
Which karat is best?
There is no single best karat; it depends on what you need. For investment, 24k bars and coins (or 22k coins such as the Sovereign and Krugerrand) give you the most gold per unit of money and the smallest dealer spread. For daily-wear rings and bracelets, 14k and 18k are harder and resist scratches and bending much better than 22k or 24k. In South Asia and the Gulf, 22k and 21k jewelry is preferred because it keeps a rich yellow colour and holds its value well when exchanged or sold.
Lower karats are not 'fake' gold; they are simply less gold. A 9k ring is real gold but only 37.5% of it, so its resale value is relatively low and most of the price you paid at retail was design and labour.
White, rose and yellow gold
Colour comes from the alloy, not from the gold itself. Yellow gold is alloyed mainly with silver and copper. Rose gold uses more copper. White gold uses palladium, nickel or manganese, and is usually plated with rhodium to give it a bright white finish. An 18k white gold ring and an 18k yellow gold ring contain the same 75% gold and have the same melt value per gram.
Testing purity when there is no mark
Unmarked gold is not worthless, but it must be tested before anyone can price it. Professional buyers use an acid test on a touchstone, an electronic conductivity tester or an X-ray fluorescence (XRF) analyser. XRF is the most accurate and does not damage the item. Be careful with magnets: gold is not magnetic, so a strongly magnetic item is not solid gold, but a non-magnetic item could still be plated brass. Until the purity is confirmed, use the lowest plausible karat in the scrap gold calculator to estimate a conservative value.
Converting between karats
If you know the weight of pure gold you want, divide by the purity to find the weight of karat gold you would need. For example, 10 grams of pure gold equals 10 ÷ 0.75 = 13.33 grams of 18k gold. Our karat converters do this for every common pair, such as 18k to 14k or 22k to 24k, and show the equivalent value at today's price.