Convert Carat to Ounce (ct → oz)

Converting carats to ounces 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 0.007055

   The conversion factor from ct to oz is 0.007055. Multiply your value by this number.
3. 3
   Read the result in ounces

   The result is your value in ounces (oz).

Multiply the value in carats by 0.007055. For the reverse direction, multiply by 141.74762.

• ✓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 Ounce?

The ounce equals exactly 28.349523125 grams or 1/16 of a pound. The word derives from the Latin 'uncia,' meaning one twelfth (the original Roman ounce was 1/12 of a Roman pound). The modern avoirdupois ounce, used for everyday weights in the United States and the United Kingdom, replaced the older Tower and Troy systems. It is the standard unit for American kitchen recipes (where 'ounce' refers to weight, distinct from the fluid ounce of volume), postal rates, package sizes (a 12-oz can of soda), and boxing-glove weights. Precious metals like gold and silver use the troy ounce (31.103 g), about 10% heavier than the avoirdupois ounce. The ounce relates to the pound (16 oz = 1 lb), the gram (1 oz ≈ 28.35 g), and the grain (1 oz = 437.5 grains).

• American and British cooking recipes
• Food packaging in the US
• Precious metals (troy ounce = 31.10 g, different from avoirdupois)