Every gold ring sold legally in Britain carries a number stamped somewhere on the inside of the band, usually too small to read without a loupe, and almost nobody buying the ring ever looks for it. That number is the only part of the ring that cannot lie. It will tell you, precisely, what you are actually wearing: 375, 750, or 916, out of a possible 999. Everything else about the piece, the shop, the setting, the price tag, is marketing. The hallmark is metallurgy.
The three numbers correspond to what most people call 9 carat, 18 carat, and 22 carat gold, and the industry has spent decades implying that higher is simply better: purer, finer, more expensive, therefore superior. It isn't that straightforward. Each carat is a different alloy with a different job. Pure gold is too soft to hold a claw setting or survive daily wear, so every carat below 24 is gold deliberately weakened with other metals to make it useful, and the question worth asking is not which carat is best but which alloy suits what you are actually going to do with it.
In Brief: Carat measures the proportion of pure gold in an alloy, out of 24 parts. 9ct (375) is 37.5% gold, harder-wearing and the most affordable; 18ct (750) is 75% gold, the standard for engagement rings and gemstone settings; 22ct (916) is 91.6% gold, soft, richly coloured, and the standard for South Asian bridal jewellery. UK law requires any gold item over one gram to carry a hallmark from one of four assay offices (London, Birmingham, Sheffield, or Edinburgh) confirming the carat is genuine.
What the number actually measures
Pure gold is 24 carat: soft, deep orange-yellow, and too pliable to hold a stone or survive a working life on a hand. To make it wearable, goldsmiths alloy it with other metals, usually copper, silver, zinc, or palladium, and the carat rating tells you what fraction of the finished metal is still gold.
- 9ct gold is 9 parts gold to 15 parts alloy: 37.5% pure gold, hallmarked 375.
- 18ct gold is 18 parts gold to 6 parts alloy: 75% pure gold, hallmarked 750.
- 22ct gold is 22 parts gold to 2 parts alloy: 91.6% pure gold, hallmarked 916.
In the UK, any gold item weighing more than one gram must be hallmarked by law, and the hallmark is applied by one of four assay offices, each with its own mark: a leopard's head for London, an anchor for Birmingham, a castle for Edinburgh, and a rose for Sheffield. The office tests the metal and stamps the piece only once the content matches what's claimed. If a ring has no hallmark and weighs more than a gram, that is worth asking about before you buy it, not after.
9ct: the workhorse, not the compromise
Nine carat gold gets treated as the budget option, which undersells what it's actually good at. With 62.5% alloy content, 9ct is harder and more scratch-resistant on the surface than the higher carats, the same trade-off that makes a knife blade harder than a coin. What that alloy content costs you is ductility: 9ct is more rigid, which means under a sharp knock it's more likely to crack than to bend. For a ring that mostly sits still, that trade-off barely matters. For a chain that gets caught on things daily, it's worth knowing.
The colour runs paler and cooler than the higher carats, closer to a champagne than a true yellow, which some people actively prefer. Over years of wear, especially with sweat, perfume, or cleaning products, the copper content can pick up a faint tarnish that a jeweller's cloth clears in a minute.
9ct is the right choice for an everyday chain that takes daily knocks, a first solid-gold piece for someone building a collection, or a signet ring bought as a starting point rather than a lifetime one. It is not a lesser version of 18ct. It is a different alloy built for a different job.
18ct: the standard, and why it became one
Eighteen carat is what most fine jewellery houses mean when they say gold, and the reason is an engineering compromise, not a marketing default. At 75% pure gold, 18ct carries enough gold to show real colour and enough alloy to hold a claw setting securely for decades. It is dense enough to feel substantial on the hand, noticeably heavier than the same design cast in 9ct, and stable enough that a well-made 18ct piece won't tarnish or corrode under normal wear.
On skin reactivity, worth being precise rather than promotional: UK and EU regulation restricts nickel in jewellery alloys specifically because nickel is the most common trigger for metal allergy, so a well-made 18ct piece sold in Britain is unlikely to cause a reaction. That is different from "completely hypoallergenic," which no gold alloy can honestly claim, since trace sensitivities to copper or palladium do exist. If you know you react to certain metals, ask what the alloy is, not just the carat.
18ct is the right choice for an engagement ring, anything with a claw or pavé setting, and any piece you're buying to keep rather than replace.
22ct: gold as it's always been worn
Twenty-two carat gold sits closest to pure, and the tradition built around it is the oldest in the trade: Mediterranean, Middle Eastern, and above all South Asian goldsmithing have worked in 22ct for centuries, and in Britain that tradition has its own high streets. Green Street in Newham and The Broadway in Southall are the two best-known clusters of specialist 22ct jewellers in London, home to established names such as PureJewels, Pakeeza Jewellers, and family-run houses like Sanjeev Jewellers, alongside larger operators including Malabar Gold & Diamonds and Joyalukkas, both of which opened Southall showrooms in the last two years to serve wedding-season demand.
The colour is the reason people seek it out specifically: a deep, warm, honeyed yellow that lower carats cannot produce, because there is not enough gold in them to produce it. The trade-off is softness. 22ct will not hold a claw or tension setting reliably, which is why bridal 22ct jewellery almost never uses the Western claw mount: stones are set using kundan (foil-backed stones pressed into a gold groove) or polki (uncut diamonds set the same way), techniques developed specifically because they don't ask the metal to grip anything under tension. A 22ct ring or bangle will show wear over years — every dent and mark of a life lived in it — which is precisely the point for jewellery bought to be worn daily and eventually passed down, rather than kept for occasions.
22ct is the right choice for a wedding set bought within that tradition, a hand-hammered bangle, or a solid band bought for its weight and colour rather than for holding a stone.
Which to actually buy
The honest answer depends on what the piece has to survive, not on which number sounds most impressive.
Buying an everyday chain or a first gold piece: 9ct. It's the most affordable entry point and its extra hardness suits daily wear.
Buying an engagement ring or anything with a set stone: 18ct. It's the only one of the three built to hold a claw setting for decades without the setting loosening.
Buying into a South Asian wedding tradition, or buying for colour and weight over stone-setting: 22ct, from a specialist rather than a general jeweller, since the kundan and polki techniques it depends on are a different skill from Western stone-setting.
Buying a signet ring: either 9ct or 18ct depending on budget, never silver as a starting material for daily wear. The signet ring edit covers engraving and maker choice in more depth once carat is decided.
Building a stack: carat matters less than consistency. Mixing 9ct and 18ct pieces on the same hand is fine visually, but be aware the softer 18ct piece will show wear faster than its 9ct neighbours. The ring stacking guide covers positioning and sizing.
Quick reference
| 9ct (375) | 18ct (750) | 22ct (916) | |
|---|---|---|---|
| Pure gold content | 37.5% | 75% | 91.6% |
| Colour | Pale, champagne | Rich, classic yellow | Deep, honeyed orange-yellow |
| Holds claw settings | Yes | Yes, the standard choice | No, needs kundan or polki setting |
| Best for | Everyday chains, entry signets | Engagement rings, gemstone pieces | Bridal sets, bangles, hand-hammered pieces |
| Where to buy specialist 22ct | General jewellers | General jewellers | Southall, Green Street, and specialist bridal jewellers |
Frequently asked questions
What does 375 stamped on gold mean?
375 is the UK hallmark for 9 carat gold, indicating the piece is 37.5% pure gold by weight. It will appear alongside a mark showing which of the four UK assay offices tested it: a leopard's head for London, an anchor for Birmingham, a castle for Edinburgh, or a rose for Sheffield. Any gold item sold in the UK weighing more than one gram is legally required to carry this mark.
Is 9ct gold real gold?
Yes. Any alloy containing at least 37.5% pure gold can legally be sold and hallmarked as gold in the UK, and 9ct is the minimum standard permitted. It is real gold combined with other metals to make it more practical for daily wear, in the same way sterling silver is silver alloyed with copper for strength.
Is 18ct gold worth the extra cost over 9ct?
For a piece you intend to keep for decades, or anything holding a claw-set stone, yes. The higher gold content gives 18ct better colour and the alloy composition is specifically balanced to hold a setting securely over years of wear. For an everyday chain that takes regular knocks, the extra cost buys colour rather than durability, since 9ct is the harder-wearing of the two.
Can 22ct gold be used for an engagement ring?
Rarely with a Western-style claw setting, because 22ct is too soft to hold a stone securely under tension long-term. It is used extensively for bridal jewellery within South Asian traditions, where stones are set using kundan or polki techniques that press the stone into a groove rather than gripping it with prongs. If you want a 22ct engagement ring, a specialist in these setting techniques, rather than a general Western jeweller, is the right place to have it made.
How can I check a gold hallmark is genuine?
Look for the full set of marks: the carat number (375, 750, or 916), the assay office symbol, and usually a sponsor's mark identifying the maker. All four UK assay offices offer services to verify a hallmark if you're unsure, and the London Assay Office at Goldsmiths' Hall provides a hallmark-tracing service for pieces bought in Britain. A piece over one gram with no hallmark at all should raise a question before a purchase, not after.
Sources: British Hallmarking Council and UK Assay Offices guidance on the Hallmarking Act 1973; Assay Office London on hallmark verification; Jewellery Outlook trade reporting on 22ct gold retail in Southall and Green Street, London, 2025.
