"Carat" on jewellery has nothing to do with diamond carat weight — it's a measure of gold purity, and it's one of the first decisions to make when choosing a piece. Here's what each common purity actually means in practice.
The three purities we work with most
- 9ct gold — 37.5% pure gold. The most durable and least expensive of the three, with a paler yellow colour because it's alloyed with more of other metals. A practical choice for pieces that see daily wear and knocks.
- 18ct gold — 75% pure gold. A middle ground: noticeably richer in colour than 9ct, while still hard enough to hold diamonds securely in a claw or pavé setting. This is why most of our diamond engagement rings are offered in 18ct.
- 22ct gold — 91.6% pure gold. A deep, warm yellow that's prized in South Asian and traditional gold jewellery. It's softer than 9ct or 18ct, so it suits chains, bangles and bracelets more than fine claw settings holding a diamond in place.
So which should you choose?
It depends on what the piece needs to do:
- Engagement or eternity rings with diamonds: 18ct gold or platinum. You want a metal hard enough to keep the stones secure over years of daily wear.
- Chains, bangles and bracelets: 22ct gold, if you want that traditional, richly coloured look and the piece won't be knocked around constantly.
- Jewellery worn every single day, all day: 9ct gold holds up well to the wear and tear, at a lower price point.
Purity and hallmarking
Every purity has its own hallmark fineness number — 375 for 9ct, 750 for 18ct, 916 for 22ct — stamped by an official UK Assay Office. We cover this in full in our guide to UK gold hallmarks.
Not sure which is right for the piece you have in mind? Browse our ring collection in your choice of metal, or get in touch and we'll talk it through.