Carat and karat relate to different elements in jewellery: diamonds and gold, respectively. Carat is a unit of measurement which is used to weigh diamonds. One carat is equal to ⅕ of a gram.  In gold, the karat (often indicated with ‘kt’ or ‘k’) denotes the purity of gold in the piece. Pure gold, which is 24kt, is most often blended with other metals in what is known as an alloy, to increase the durability and affordability of the piece. The higher the karat number, the higher the percentage of pure gold. 14kt and 18kt gold are the most popular choices for engagement ring settings.