What does carat mean?
A carat is a standard unit of measurement with two distinct commercial uses: it weighs precious stones and gauges the purity of gold. As a unit of mass, one carat equals exactly 200 milligrams, so a five-carat diamond weighs one gram. As a measure of gold purity, carats are expressed in parts out of 24 — pure gold is 24-carat, while 18-carat gold contains 18 parts gold and 6 parts other metals. The word derives from the Greek keration, meaning a small carob seed; ancient jewelers used these seeds as counterweights because of their consistent size. Today the carat is central to the jewelry trade, where even fractions of a carat can dramatically affect a stone's price. Because the word sounds identical to 'carrot,' the vegetable, careful spelling matters, and its sibling term 'karat' applies specifically to gold rather than to gemstones.
nounA carat is a unit of weight for gemstones and pearls, equal to 200 milligrams (one-fifth of a gram). The term also refers to a measure of the purity of gold, expressed in parts out of 24.
- A unit of mass for gemstones and pearls, equal to 200 milligrams.
- A measure of the fineness (purity) of gold, expressed as parts per 24.
"She chose a two-carat diamond for her engagement ring."
"The jeweler weighed the sapphire and found it just over three carats."
"The ring was stamped 18-carat, meaning three-quarters pure gold."
Standard pluralization; used when stating total combined weight, e.g. of multiple stones.
"The bracelet contains twelve carats of diamonds in total."
The carat got its name from carob seeds, which ancient traders used as counterweights because they were so remarkably uniform in weight.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of carat
The word 'carat' comes via French from Italian 'carato,' which traces back through Arabic 'qīrāṭ' to the Greek 'keration,' meaning a small carob seed. Carob seeds were used by ancient merchants as tiny standard weights when weighing gems and gold. A related borrowing from the same Arabic root gave English the word 'quarantine,' which originally denoted a period of forty days. The spelling variant 'karat' is now chiefly used in American English for the gold-purity sense.
Related word forms
How carat is actually used
In American English, 'karat' is the standard spelling for the gold-purity sense, while 'carat' is reserved for gemstone weight; British English typically uses 'carat' for both. The abbreviation 'ct' denotes gemstone weight and 'kt' or 'K' denotes gold purity.
Easily confused with carat
'Carat' measures gemstone weight, while 'karat' (abbreviated kt or K) measures the purity of gold on a scale where 24 karats is pure gold.
A carrot is an edible orange root vegetable, whereas a carat is a unit of measurement for gems and gold — they differ only in spelling.