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9ct, 14ct, 18ct – you’ve probably seen these on jewellery labels or tiny stamps inside a ring. But what does the number actually tell you, and why do two rings that look almost the same contain very different amounts of gold? Here’s a plain-English guide to gold carats, with the fineness marks you’ll find on Irish jewellery.
What is a carat?
Think of a piece of gold jewellery as being made of 24 equal parts. The carat tells you how many of those parts are pure gold. The rest is other metals – usually silver, copper, zinc or palladium – added to make the gold stronger and to change its colour.
So 18ct means 18 parts gold and 6 parts other metals. To turn a carat into a percentage, divide by 24: 18 ÷ 24 = 0.75, or 75% gold. In Ireland and Britain carat is written ct; in America you’ll often see K or kt instead, but they mean the same thing.
Pure gold is beautiful but very soft. It scratches and bends easily, which is why most everyday jewellery is a mix. A lower carat means a harder-wearing piece – and less pure gold.
The carats one by one
Each card shows the 24 parts of the piece, with the gold parts in yellow, and the fineness mark you’d find in the hallmark.
9ct
375
9 of 24 parts gold · 37.5%
About a third pure gold. Hard-wearing and widely used for everyday rings, chains and earrings.
14ct
585
14 of 24 parts gold · 58.5%
More than half pure gold. A popular middle ground for everyday rings and chains.
18ct
750
18 of 24 parts gold · 75%
Three quarters pure gold. A richer colour, often chosen for engagement and wedding rings.
22ct
916
22 of 24 parts gold · 91.6%
Almost pure. Deep yellow and soft – seen in traditional wedding bands and in gold coins.
24ct
999
24 of 24 parts gold · 99.9%
Pure gold. Too soft for most jewellery, so it’s mainly used for bars and coins.
You may also come across less common marks. The Assay Office in Dublin Castle also hallmarks 417 (10ct), 833 (20ct) and 990 gold. In everyday jewellery, though, 9ct, 14ct and 18ct are the ones you’ll see most often.
9ct vs 14ct vs 18ct vs 22ct: side by side
| Carat | Mark | Pure gold | Colour | Wear |
|---|---|---|---|---|
| 9ct | 375 | 37.5% | Paler yellow | Very hard-wearing; can tarnish slightly |
| 14ct | 585 | 58.5% | Warm yellow | Hard-wearing |
| 18ct | 750 | 75% | Rich yellow | Softer; shows scratches more |
| 22ct | 916 | 91.6% | Deep yellow | Soft; bends and scratches easily |
| 24ct | 999 | 99.9% | Deep orange-yellow | Very soft; rarely used for jewellery |
White, rose and yellow gold: same carat, different mix
Colour and carat are two separate things. An 18ct white gold ring and an 18ct yellow gold ring both contain 75% pure gold – the difference is in the other 25%. White gold is mixed with white metals such as palladium or silver and is often coated with rhodium for extra shine. Rose gold gets its pink tone from extra copper. Yellow gold uses a balance of silver and copper.
That’s why you can’t tell a piece’s carat from its colour alone. A pale 9ct chain and an 18ct white gold ring can look very different from what you’d expect – the fineness mark is the reliable guide.
What carat means for value
When gold jewellery is valued for its material, what counts is the amount of pure gold it contains. That depends on two things: how much the piece weighs, and its carat. Two rings of exactly the same weight can therefore contain very different amounts of gold:
10 g ring · 9ct
10 g × 37.5%
3.75 g
pure gold
10 g ring · 18ct
10 g × 75%
7.5 g
pure gold
The example shows gold content only – it isn’t an offer.
The 18ct ring contains twice as much pure gold as the 9ct ring, even though they weigh the same. The third factor is the price of gold on the day.
An offer for used jewellery isn’t the same as the world market price you see in the news. That price is for pure, refined gold, and jewellery has to be melted and refined before the gold can be used again. Condition doesn’t change the gold content: a scratched or broken 18ct ring still contains the same amount of gold as before.
Gold carats vs diamond carats
Not sure what carat your gold is?
Look for the fineness mark inside a ring band, on a clasp or on the back of a pendant. Irish hallmarks also include the Hibernia figure and a sponsor’s mark. Our guide to recognising genuine gold at home shows what to look for, and which home checks to trust.
If the mark is worn or missing, a Gold Expert can test the piece during a free, private valuation of about 15 minutes at a local stop. You see every step, and you decide afterwards whether to sell anything. If you do, payment is made by bank transfer no later than the fifth banking day – we never pay in cash. Read more about what happens during a gold valuation.
Frequently asked questions about gold carats
Is 9ct gold real gold?
Yes. 9ct gold contains 37.5% pure gold, and it’s hallmarked as gold in Ireland. The rest is other metals that make it harder-wearing.
Which is better, 9ct or 18ct?
It depends on what you want. 18ct contains twice as much pure gold and has a richer colour, while 9ct is harder-wearing and more affordable. For material value, more pure gold means a higher value at the same weight.
What does 585 mean on gold?
It’s the fineness mark for 14ct gold: 585 parts per thousand, or 58.5%, is pure gold.
Does white gold have a lower carat than yellow gold?
No. White and yellow gold come in the same carats. An 18ct white gold ring contains the same 75% pure gold as an 18ct yellow one – only the other metals differ.
Why isn’t most jewellery 24ct?
Pure gold is very soft, so it scratches and bends easily. Mixing it with other metals makes jewellery strong enough to wear every day.
Sources
- Assay Office Ireland: Hallmarking legislation (approved gold fineness marks)
- Assay Office Ireland: Compulsory hallmarks
Checked 12 October 2026.
