UK Gold Purity Guide — 9ct, 14ct, 18ct, 22ct, 24ct
Every piece of UK gold jewellery carries a tiny stamp telling you how pure it is. This guide explains the five carats you'll see — what each means, what they're worth, which one to buy for what, and how to read a UK hallmark.
The five carats at a glance
| Carat | Purity | UK hallmark | Where you'll see it |
|---|---|---|---|
| 9ct | 37.5% | 375 | Most UK high-street jewellery, scrap. |
| 14ct | 58.5% | 585 | US standard, increasingly common in UK fine jewellery. |
| 18ct | 75.0% | 750 | Engagement rings, premium designer pieces. |
| 22ct | 91.6% | 916 | Sovereigns and most South Asian / Middle Eastern jewellery. |
| 24ct | 99.9%+ | 999 | Investment bullion: Britannias, Krugerrands, bars. |
What "carat" actually means
One carat (also spelled "karat" in US English) is 1/24th of pure gold. So:
- 24ct = 24/24 = 100% pure gold (rounded; in practice .999 or .9999 is treated as "fine").
- 22ct = 22/24 = 91.67% pure gold.
- 18ct = 18/24 = 75% pure gold.
- 14ct = 14/24 ≈ 58.33% pure gold (hallmarked 585 by convention).
- 9ct = 9/24 = 37.5% pure gold.
The remaining percentage is alloy — usually copper, silver, sometimes palladium or zinc — added to make gold hard enough to actually wear without bending out of shape.
Why isn't all jewellery 24ct?
Pure gold is soft. Hilariously soft for jewellery purposes — you could dent a pure gold ring with your fingernail. Adding even a small amount of alloy dramatically improves hardness, scratch resistance and durability. The trade-off:
- Higher carat = richer yellow colour, hypoallergenic, but soft, scratches easily, can bend
- Lower carat = harder, holds shape, more wear-resistant, but paler colour and the alloy metals can cause skin reactions in some people
9ct is a fair compromise for everyday rings and chains. 18ct is the sweet spot for fine jewellery — durable enough to wear daily, but rich enough in gold to look unambiguously like gold. 22ct is too soft for most rings, which is why you'll mostly see it in coins, bangles and ceremonial pieces.
How to read a UK hallmark
UK law requires hallmarking on most gold items weighing more than 1g. A full UK hallmark has up to five parts:
- Sponsor's mark — the maker or sponsor, 2–3 initials in a shaped border
- Standard mark — a stamp showing purity in a shaped surround (e.g. an oval for gold)
- Millesimal fineness — three digits showing parts per thousand (375, 585, 750, 916, 999)
- Assay office mark — anchor (Birmingham), leopard's head (London), rose (Sheffield), castle (Edinburgh)
- Date letter — single letter in a shaped surround, cycle of 25, indicating year of assay
Optional commemorative marks may also appear (Coronation marks, Millennium marks, etc.). Older pieces may only show the fineness and assay office.
Which carat for which purpose?
- Investment / store of value: 22ct sovereigns or 24ct Britannias. Both are CGT-exempt UK legal tender.
- Wedding band / daily-wear ring: 18ct for the right balance of durability and look. 14ct if you're rough on your hands.
- Engagement ring: 18ct platinum-look (white gold with rhodium plating) or 18ct yellow. 9ct only if budget is the priority — it will dull and scratch faster.
- Chain or pendant: 9ct for everyday, 18ct for something heirloom-quality.
- Gift / occasional wear: 22ct if you want maximum gold content per gram visible.
Live per-gram pricing for each carat
Each purity links to a focused calculator with live spot price and worked examples:
- 9ct gold price per gram — UK high-street jewellery
- 18ct gold price per gram — engagement rings, premium pieces
- 22ct gold price per gram — sovereigns, Asian jewellery
For 14ct or 24ct, use the main calculator with the appropriate purity selected.