A karat (K or kt) is a unit of gold purity.
- 24 karat = pure gold (or as close as we practically get)
- 18 karat = 18/24 gold = 75% gold
- 14 karat = 14/24 gold ≈ 58.3% gold, etc.
So a karat is 1/24th part of the whole in terms of gold content by weight in the alloy.
In contrast: carat with a “c” is a unit of mass for gemstones, equal to 0.2 grams.
- Verifying the statement about “carat” (with a c)
Yes, this is correct:
- The metric carat is defined as a unit of mass equal to 200 milligrams = 0.2 grams, used for weighing gemstones and pearls. (Wikipedia)
Multiple authoritative sources (Wikipedia, GIA, American Gem Society, and others) all give the same definition:
1 carat = 200 mg = 0.2 g, the standard unit of weight for diamonds and most gemstones. (Wikipedia)
So your original line:
“carat with a ‘c’ is a unit of mass for gemstones, equal to 0.2 grams”
is accurate.
- Why do British/“English” gold sellers use carat instead of karat? Are they ignorant?
Short answer: no, they’re not ignorant—they’re just following British English and older historical usage.
Key points:
- In British English, carat is used for both:
- the mass of gemstones, and
- the purity of gold. (QuillBot)
- In American English, the convention split:
- carat → gemstone weight
- karat → gold purity (merriam-webster.com)
Some more detail:
- Reference guides explicitly say that British English prefers “carat” and American English prefers “karat” for gold purity. (QuillBot)
- The word “carat” predates “karat”; “karat” was introduced later (primarily in the US) to make a clearer distinction between gemstone weight and gold purity. (Larsen Jewellery)
- Technical and trade sources describe gold purity as “carat (UK) or karat (US), parts of pure gold out of 24”—so both spellings are recognized as standard, just regionally different. (Wikipedia)
In the UK jewelry and bullion trade you’ll routinely see:
- “9ct, 18ct, 22ct, 24ct gold” (all spelled carat/ct) in catalogs and hallmarking explanations. (ukbullion.com)
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