A carat is a measure of gold purity on a scale of 24: 24 carat is pure gold, 18 carat is 18 parts gold in 24 (75%), and 9 carat is 37.5% gold. In the UK it is written "ct", for example 9ct or 22ct.
Carat to fineness conversion
Divide the carat number by 24 to get the share of gold, then multiply by 1,000 for fineness. The UK hallmarks the result as a three digit number.
| Carat | Gold content | UK hallmark | Where you see it |
|---|---|---|---|
| 9ct | 37.5% | 375 | The most common UK jewellery standard |
| 14ct | 58.5% | 585 | Imported and some UK jewellery |
| 18ct | 75% | 750 | Engagement and wedding rings |
| 22ct | 91.67% | 916 | Sovereign, older Britannias, some jewellery |
| 24ct | 99.9% or more | 999 / 990 | Bullion bars and modern bullion coins |
Do not confuse the gold carat with the carat used for gemstones, which is a weight of 0.2 g. A "1 carat diamond" says nothing about the gold in the ring.
Jewellery vs bullion
9ct jewellery is popular in the UK because it is hard wearing and affordable, but most of the piece is copper and silver. When you sell it, you are paid for the gold content only, minus the buyer's margin. Example: a 9ct chain weighing 10 g holds 10 x 0.375 = 3.75 g of gold. An 18ct ring of the same weight holds 7.5 g.
Jewellery is also charged 20% VAT when new and carries design and retail costs, so the price per gram of gold is far higher than for bullion. If your goal is to own gold rather than wear it, coins and bars give you much more metal for the money. Check today's gold price per gram in sterling to see what the raw metal in a piece is worth.
Why the Sovereign is 22 carat
The Royal Mint has struck the Sovereign in 22 carat gold since 1817. The alloy is tougher than pure gold, which mattered for a coin that once circulated. The gold Britannia was also 22 carat until 2013, when The Royal Mint moved it to 999.9 fine gold (24 carat). Both versions hold the same fine weight per stated ounce, so the carat does not change the gold you own, only how the coin looks and wears.
For investing, carat matters less than the fine weight in troy ounce terms and the premium over spot. Compare the delivered prices of 22ct and 24ct gold coins on one list to see which gives you more gold per pound.
Related terms
FAQ
Is 9ct gold real gold?
Yes, 9ct gold is real gold alloy containing 37.5% pure gold, and it must carry a 375 hallmark in the UK if it weighs 1 gram or more.
What carat is a gold Sovereign?
A Sovereign is struck in 22 carat gold, which is 916.7 parts per thousand.
Is 24ct gold better than 22ct for investing?
Not in itself. What counts is the fine gold content and the price you pay for it; a 22ct Sovereign and a 24ct bar of the same fine weight hold the same gold.