What does carat mean for diamonds and gemstones?
By Jared James · Last updated 24 August 2026
Definition
For diamonds and other gemstones, carat is a unit of weight equal to 200 milligrams, or one fifth of a gram. A higher carat weight usually means a larger stone, but cut shape and proportions determine how large it looks from above. Two diamonds with the same carat weight can therefore have different visible dimensions. Gold purity also uses the spelling carat in Australia, but that is a separate meaning covered in the linked gold guide.
Frequently asked questions
- Is carat the same as karat?
- For gemstones, carat means weight and karat is not used. For gold, carat and the American spelling karat both describe purity out of 24. The linked gold guide explains that separate use.
- Does a higher carat diamond look bigger?
- A higher carat weight means the stone is heavier, and a heavier stone is usually physically larger too, though shape affects how big a stone looks face-up. A well-cut 1-carat round brilliant will look noticeably larger than a poorly cut stone of the same weight.
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