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Carat (gemstone) to Gram

ct
Gram (g)
g

g = ct × 0.200000

Quick Reference: Carat (gemstone) to Gram

ctg
0.10.02
0.50.1
10.2
20.4
51
102

How to Convert Carat (gemstone) to Gram

Formula:

g = ct × 0.200000

Example:

0.5 ct = 0.1 g

  1. Enter the value in Carat (gemstone) you want to convert
  2. The result is calculated automatically
  3. Copy your result in Gram or continue converting

About Carat (gemstone) and Gram

The metric carat (ct) is the standard unit for gemstone weight. One carat equals exactly 0.2 grams — a definition adopted internationally in 1907. Not to be confused with "karat" (gold purity). Diamond, ruby, sapphire, and emerald weights are always described in carats.

Common Uses for This Conversion

Essential for diamond buyers comparing stone sizes, jewelers and gemologists, online jewelry shopping, customs declarations for gemstone imports, and insurance appraisals. A 1-carat round diamond is approximately 6.5 mm in diameter.

💡Did You Know?

The word "carat" comes from the carob seed (Ceratonia siliqua), historically used as a reference weight due to its remarkably consistent mass of about 0.2 grams. Surat, India, cuts and polishes over 90% of the world's diamonds.

Frequently Asked Questions

One carat equals exactly 0.2 grams (200 milligrams). This is the international metric carat definition adopted in 1907. So 5 carats = 1 gram, and 50 carats = 10 grams. This is the gemstone carat — not to be confused with the karat measuring gold purity.
1 gram equals exactly 5 carats (since 1 ct = 0.2 g exactly). A 1-gram diamond would be 5 carats and is extremely rare and valuable. For reference, a 1-carat round diamond has a diameter of about 6.5 mm.
"Carat" (ct) measures the weight of gemstones: 1 ct = 0.2 grams. "Karat" (k or kt) measures the purity of gold: 24k = pure gold, 18k = 75% gold. They are completely different units despite sounding similar. Never use them interchangeably.
A 0.5 carat (half-carat) diamond weighs exactly 0.1 grams (100 milligrams). A round half-carat diamond is typically about 5.1 mm in diameter. Half-carat diamonds are one of the most popular engagement ring sizes.

Related Conversions

Kilogram → PoundPound → KilogramGram → OunceOunce → GramKilogram → StoneStone → KilogramTroy Ounce → GramGram → Troy OunceGram → Carat (gemstone)Grain → GramGram → GrainPennyweight → GramGram → Pennyweight

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