TL;DR: gold purity is expressed differently in different countries. The UK commonly uses carats, such as 9ct and 18ct, while North America uses karats, such as 10k, 14k and 18k. The numbers describe how much of the metal is pure gold: 10k is about 41.7 per cent gold, 14k about 58.3 per cent, 18k 75 per cent and 9ct 37.5 per cent. Higher purity is softer and richer in colour, and lower purity is harder. We state the metal and purity in writing for every design. Pieces start from £600.
The numbers explained
Pure gold is 24 carat. The number tells you how many parts out of 24 are gold, so 18 carat is 18 parts gold and 6 parts other metals, which is 75 per cent. The same arithmetic gives 14 as 58.3 per cent, 10 as 41.7 per cent and 9 as 37.5 per cent. Fineness numbers stamped on jewellery show the same thing in parts per thousand, so 750 means 18 carat, 585 means 14 carat, 417 means 10 carat and 375 means 9 carat.
Carat and karat
Carat and karat describe gold purity in the same way, but carat is also used for the weight of a gemstone, which is a different measurement. The spelling karat is used in North America for gold, which helps avoid confusion. A one carat diamond is a weight of stone, not a gold purity.
Comparing the grades
- 9ct: 37.5 per cent gold, hard and affordable, paler in colour.
- 10k: 41.7 per cent gold, hard wearing, popular in North America.
- 14k: 58.3 per cent gold, a balance of durability and richness.
- 18ct or 18k: 75 per cent gold, richer colour, a little softer.
The right choice depends on how you wear the ring, your skin and your preferences. Higher purity gold has a deeper colour but can scratch more easily. Lower purity is tougher but contains more alloy metals, which can affect skin that reacts to some metals.
Which suits which person
- You want the richest colour: 18ct or 18k, with a little more care for scratches.
- You want a balance: 14k is a common middle path in North America.
- You are hard on jewellery: a lower purity is tougher, though a well made higher purity ring can still suit daily wear.
- You have sensitive skin: tell us, so we can talk through the metals and what they are alloyed with.
What we use
Tell us which metal and purity you would like, and we will explain the choices. We state the metal and purity in writing when we quote your design, and our guide to reading your invoice and certificate explains how to read the details. You can also read our guide to comparing metals for rings.
Colour and care
Yellow, white and rose gold are made by mixing gold with different metals. White gold is often finished with a bright coating that can wear, and our guide to polishing or replating explains what to expect over time.
Ordering from abroad
If you are used to 10k or 14k, do not assume that a UK 9ct or 18ct is the same as the grade you know. Tell us what you are used to and we will explain the nearest equivalent in plain terms. The customer pays import duty and tax, which differ by country.
Frequently asked questions
Is 14k the same as 9ct?
No. 14k is about 58.3 per cent gold and 9ct is 37.5 per cent.
What is 750 gold?
It is 18 carat gold, 75 per cent pure.
Which is best for an engagement ring?
It depends on how you wear it. 18ct is richer in colour, while lower purity is harder.
Will you state the purity in writing?
Yes, for every design.