Convert Carat to Gram (ct → g)

Converting carats to grams is straightforward: multiply by the conversion factor. Follow these three steps to do it by hand or in your head.

1. 1
   Take your value in carats

   Start with the number of carats (ct) you want to convert.
2. 2
   Multiply by 0.2

   The conversion factor from ct to g is 0.2. Multiply your value by this number.
3. 3
   Read the result in grams

   The result is your value in grams (g).

Multiply the value in carats by 0.2. For the reverse direction, multiply by 5.

• ✓1 carat = 200 mg = 0.2 g exactly since 1907.
• ✓Carat (gem weight) and karat (gold purity, 24 K = pure) are different words with different meanings.
• ✓A carat is divided into 100 points; a 0.25 ct diamond is called a "25-pointer".

• ✗Confusing carat (mass) with karat (gold purity).
• ✗Assuming a 2-carat diamond is twice the physical size of a 1-carat — volume scales with cube root of mass.
• ✗Using "karat" on gemstone certificates — international standard is "carat" spelled with a C.

What is the Carat?

The carat equals exactly 200 milligrams (0.2 g) and is the universal unit for gemstone and diamond weight in the global jewelry industry. The word derives from the Greek 'keration' and the Arabic 'qīrāṭ,' both referring to carob seeds, which were once used as natural counterweights for weighing gems because they have remarkably uniform mass. The metric carat was standardized in 1907 at exactly 200 mg, replacing dozens of regional carat values that had varied between 188 and 213 mg. A 1-carat diamond is roughly 6.5 mm in diameter, and the famous Hope Diamond weighs 45.52 carats. The carat is distinct from the karat (with a 'k'), which measures gold purity (24-karat = 100% gold). It relates to the gram (5 ct = 1 g) and the milligram (200 mg = 1 ct). Gem dealers commonly use 'points' for fractions (100 points = 1 carat).

• Diamond and gemstone retail and valuation
• Jewellery manufacturing and design
• International gem certification (GIA, IGI)

What is the Gram?

The gram equals one thousandth of a kilogram (0.001 kg) and is the everyday metric unit for cooking ingredients, postage, jewelry, pharmaceuticals, and small product weights. Originally defined in 1795 as 'the absolute weight of a volume of pure water equal to a cube of one hundredth of a meter at the temperature of melting ice,' the gram is now formally defined via the kilogram. It relates simply to the milligram (1,000 mg = 1 g) and the kilogram (1,000 g = 1 kg). European nutrition labels universally use grams for ingredient quantities, and recipes worldwide outside North America measure ingredients by mass in grams rather than by volume. Gold and silver are traded in grams for small quantities, while gemstones use carats (0.2 g = 1 carat). A standard paper clip weighs about 1 g.

• European cooking and baking recipes
• Over-the-counter medication dosages
• Gold, silver and gemstone retail (per gram pricing)