Carat vs Karat: The Difference in One Minute

Carat is a unit of mass for gemstones. GIA defines 1 metric carat as 200 milligrams, or 0.2 grams. Each carat is split into 100 points, so a 0.50 ct diamond is a 50-point stone. Carat is weight, not size: two 1 ct diamonds of different cuts can look different in size from the top.

Carat	Grams	Points	Round diamond, approx. diameter
0.25 ct	0.05 g	25	about 4.1 mm
0.50 ct	0.10 g	50	about 5.2 mm
1.00 ct	0.20 g	100	about 6.5 mm
2.00 ct	0.40 g	200	about 8.2 mm
5.00 ct	1.00 g	500	about 11 mm

Our house ring Round Lab Diamond Ring 4.62 ct, 14K Yellow Gold ($2,800) carries 4.62 ct of lab diamond in total. That whole diamond load weighs about 0.92 grams, less than a paperclip.

Karat measures how much of a metal is pure gold, out of 24 parts. The rest is alloy, such as copper, silver, zinc or palladium, added for strength and color. Under the FTC Jewelry Guides, a karat mark has to tell the truth about the gold content, and gold jewelry should be marked with its karat.

Karat	Parts gold	Gold content	European stamp
10K	10 of 24	41.7%	417
14K	14 of 24	58.3%	585
18K	18 of 24	75%	750
22K	22 of 24	91.7%	916
24K	24 of 24	99.9%	999

Lower karat means harder and more scratch-resistant; higher karat means richer color and softer metal. Our gold karat guide and what 14K means go deeper.

Most jewelry listings show both numbers. Read them as two separate facts: the metal, then the stones.

• Round Lab Diamond Bracelet 7.49 ct, 10K White Gold ($2,200): 10K white gold (41.7% gold) holding 7.49 ct of lab diamonds in total.
• Round Lab Diamond Necklace 9.18 ct, 14K White Gold ($5,300): 14K white gold (58.3% gold) with 9.18 ct total.
• Round Natural Diamond Ring, 18K White Gold ($6,000): 18K white gold (75% gold) with a natural diamond graded E color, VS1.
• Rope Chain 3mm ($2,175): 10K gold, no stones, so no carat number at all.

When a piece has many stones, the carat figure is almost always total carat weight. Learn how that number is built in what total carat weight means.

Both numbers change what a piece costs, in different ways. Karat sets how much pure gold is in the metal. The weight of pure gold in a piece is simply the metal weight times the karat fraction.

Piece weighing 20 g	Pure gold inside
10K	8.3 g
14K	11.7 g
18K	15.0 g

So moving from 10K to 14K on the same design adds about 40% more pure gold. Carat works differently: diamond prices rise faster than weight, because large stones are rarer. A 2 ct stone of the same grade usually costs well over twice a 1 ct stone. That is why total carat weight split across many small stones, as in a diamond necklace, costs much less per carat than one big center stone of the same total weight.

Plain gold chains do not have a carat number at all, because there is no stone. They are described by karat, width in millimeters and length, and sometimes by weight in grams. A gold chain listed as 10K, 3 mm, 22 inches tells you everything that matters. Iced pieces and diamond watches list carat as a total across dozens or hundreds of small stones. When you see a large carat number on a necklace or bezel, it is the sum of many small stones, not one big one, and it is priced that way.

• "14 carat gold." Outside the US, especially in the UK, carat is also used for gold purity. In US jewelry, gold uses karat (K) and stones use carat (ct).
• "A 10K diamond." Diamonds do not have karats. The 10K describes the gold.
• Carat vs size. A shallow oval can look bigger than a deep round of the same weight.
• Total vs center. A "3 ct ring" may have a 2 ct center and 1 ct of side stones. Ask for the center stone weight.
• Carrot. Spelling mistake, common in searches. Same as carat.

Both words trace back to the carob seed, once used as a small counterweight by traders. Gem dealers kept the seed as a unit of weight, which became the metric carat in the early 20th century. Gold traders used the same root for a fraction of 24, from an old coin system. American English split the spelling: carat for stones, karat for gold.

	Carat	Karat
Abbreviation	ct	K or kt
Measures	Weight of a gemstone	Purity of gold
Scale	1 ct = 0.2 g = 100 points	Parts out of 24
Higher means	Heavier stone	More pure gold, softer metal
Applies to	Diamonds, gemstones, pearls	Gold only

Want the rest of the vocabulary? Start with the jewelry glossary, then the diamond 4Cs guide. To check a stamp on a piece you own, see hallmarks and gold stamps.