The main difference is gold content: 9ct is 375 parts gold per thousand, 14ct is 585 and 18ct is 750. That changes price, colour and the proportion of alloying metals.
| Gold | Fineness | Pure gold | Good fit for |
|---|---|---|---|
| 9ct | 375 | 37.5% | Value-focused everyday jewellery |
| 14ct | 585 | 58.5% | Middle ground between purity and cost |
| 18ct | 750 | 75% | Higher gold content and luxury jewellery |
Which is most durable?
Purity alone does not tell the whole durability story because alloy recipes, construction and how an item is worn matter. Lower-carat alloys contain more non-gold metal, but a poorly made 9ct piece can still be less practical than a well-made 18ct one.
Which looks most golden?
18ct yellow gold commonly has a richer yellow appearance because of its higher gold content, though alloy composition can shift colour. White and rose gold deliberately use alloying metals to change appearance.
Which offers the best value?
For frequent wear on a budget, 9ct can make sense in the UK. 14ct offers a middle ground between gold content and cost. 18ct suits buyers prioritising higher gold content. Compare actual weight, construction and workmanship rather than carat alone.
9ct: practical UK entry point. 14ct: useful middle ground. 18ct: higher gold content and typically higher material cost. None is automatically the best-made piece.
UK hallmark shortcut
Look for fineness numbers such as 375, 585 or 750 as part of a proper hallmark where hallmarking is required. A complete UK hallmark contains more than the fineness number; see How to Read UK Gold Hallmarks.