+44 20 351 466 05
+49 89 1222 893 0


Carat weight for gemstones

The international gem industry generally uses the term 'carat' as a unit of weight. Carat (sometimes abbreviated to ct. and also known as karat) have been used as a unit of measurement in gem trading since ancient times. The word is probably derived from 'kuara', the seed of the African coral tree. A carat is subdivided into decimal fractions (e.g. 0.75 ct) to two decimal places. Carat weight for gems should not be confused with carat as a measure of purity for gold.

Carat purity for gold

In gold jewellery, the carat is not a unit of weight but a designation of quality. The higher the number of carat of a piece of jewellery, the higher its proportion of pure gold. Two pieces of jewellery may therefore have the same number of carat yet differ widely in weight.

The carat rating of gold describes its purity and is expressed in fractions of 24 or 1000. Theoretically, pure gold contains 24/24 parts of gold – in other words, 1000 parts.

Jewellery makers work with alloys, mixing gold with other metals to achieve the desired colours and degrees of hardness. For example, highly coveted rose gold is made by mixing copper with pure gold.

Premium jewellers generally use alloys with the following proportions of pure gold: 750 gold = 18 carat and 585 gold = 14.04 carat.

At RenéSim we use by default 18-carat gold, containing 750 parts per thousand of pure gold.


About RenéSim Service Ring Sizes Newsletter Press Jobs Terms and Conditions Privacy Policy Credits and Legal Notice

renesim GmbH

Branch office (appointment only):
16 Hanover Square, Mayfair
W1S 1HT London, United Kingdom
T +44 20 351 466 05

Amiraplatz 1, D-80333 Munich
T +49 89 1222 893 0

Hours Mon - Fri 8 am - 6 pm


Subscribe to our newsletter
to receive regular information
and interesting news:

Newsletter Subscription

Find RenÉSim here too
100% Satisfaction guarantee
  • 180 years of family craftsmanship in the jewellery business
  • 30-day right of return
  • Supreme quality and top service
  • Free ring size adjustment
  • Personal customer care and high availability
  • Secure payment and free shipping from Munich
Our carriers are
Payment methods
As an online jeweller, RenéSim combines the benefits of a modern online-based business model with 180 years of family-run traditional craftsmanship in the jewellery industry. Gemstones such as diamonds are the central focus at RenéSim; we supply high-quality, thoroughly individual pieces such as engagement rings in addition to loose diamonds. We offer unique diamond post earrings, diamond rings, memory rings, engagement rings and much more. Consult the jewellery experts at RenéSim!

Copyright © 2010 - 2017 RenéSim - Online Luxury Jeweller