How many milligrams are in one carat?

One carat equals exactly 200 milligrams. This is not an approximation - the metric carat is defined as 200 mg.

How is the carat subdivided?

The carat is divided into 100 'points.' One point equals 2 milligrams. A '50-point diamond' is 0.5 carats (100 mg), and a '25-point diamond' is 0.25 carats (50 mg). This point system allows jewelers to avoid decimal notation.

Is a carat the same as a karat?

No. A carat (ct) measures gemstone weight (200 mg). A karat (kt or K) measures gold purity - 24 karat means pure gold, 18 karat means 75% gold. They share an etymological root (carob seeds) but are completely different measurements.

Carats to Milligrams (ct to mg) Converter

1 ct = 200 mg

1 Carat equals 200 Milligrams (1 ct = 200 mg). Convert Carats to Milligrams with formula, table, and examples.

One carat equals exactly 200 milligrams. This is the defining relationship of the modern metric carat, established by international agreement in 1907. The milligram conversion is the most fundamental one for the carat, since the carat was literally defined as 200 milligrams. No rounding, no approximation - a clean, exact 200.

How to Convert Carats to Milligrams

mg = ct × 200

Multiply the value in Carats by 200

Take your value in Carats
Multiply by 200
Read the result in Milligrams

Common Carats to Milligrams Conversions

Carats (ct)	Milligrams (mg)	Status
0.01 ct	2 mg
0.05 ct	10 mg
0.1 ct	20 mg
0.25 ct	50 mg
0.5 ct	100 mg
0.75 ct	150 mg
1 ct	200 mg
1.5 ct	300 mg
2 ct	400 mg
3 ct	600 mg
5 ct	1,000 mg
10 ct	2,000 mg
25 ct	5,000 mg
50 ct	10,000 mg
100 ct	20,000 mg
500 ct	100,000 mg

Good to Know About Carats to Milligrams Conversion

Before the 1907 standardization, the carat varied by country and sometimes by city. The Florentine carat was about 197 mg, the London carat 205 mg, and the South African carat 206 mg. International gemstone trade was plagued by these discrepancies. The adoption of a universal 200 mg carat was one of the earliest successful acts of global measurement standardization, predating many other international standards.

Carats to Milligrams: What You Need to Know

Jewelers use milligrams when carat notation is insufficient for very small stones. A 10-point diamond (0.1 carat) weighs exactly 20 milligrams. Pharmaceutical scales that measure in milligrams can double as gem-weighing instruments for small accent stones and melee diamonds. Gemological laboratories like the GIA report weights to the nearest milligram when grading stones below 0.5 carats.

What is a Carat? ct

A carat is a unit of mass equal to exactly 200 milligrams (0.2 grams), used for measuring gemstones and pearls. Adopted internationally in 1907 by the Fourth General Conference on Weights and Measures.

Metric diamond weight gemstone grading pearl measurement

Learn more about Carat →

What is a Milligram? mg

A metric unit of mass equal to one thousandth of a gram, or one millionth of a kilogram. Commonly used in medicine and pharmacology.

Metric medicine pharmacology nutrition

Learn more about Milligram →

Going the other way? Use our Milligrams to Carats converter.

Carats to Milligrams FAQ

One carat equals exactly 200 milligrams. This is not an approximation - the metric carat is defined as 200 mg.
The carat is divided into 100 'points.' One point equals 2 milligrams. A '50-point diamond' is 0.5 carats (100 mg), and a '25-point diamond' is 0.25 carats (50 mg). This point system allows jewelers to avoid decimal notation.
No. A carat (ct) measures gemstone weight (200 mg). A karat (kt or K) measures gold purity - 24 karat means pure gold, 18 karat means 75% gold. They share an etymological root (carob seeds) but are completely different measurements.

Non-Frequently Asked Questions About Carats to Milligrams

Questions nobody should ask - but someone did.

Exactly the same. A standard 200 mg ibuprofen tablet and a 1-carat diamond are identical in weight. The difference in value is somewhat significant: the tablet costs a few cents, while the diamond costs several thousand dollars. Swallowing the wrong one would be regrettable.
An average mosquito weighs about 2.5 milligrams, which is 0.0125 carats - roughly one-eightieth of a carat. So a swarm of 80 mosquitoes weighs as much as a 1-carat diamond. The mosquitoes are considerably less desirable at a dinner party.
A single grain of granulated sugar weighs about 625 micrograms or 0.625 milligrams, which is 0.003125 carats. You would need to lick about 320 individual sugar grains to consume one carat's worth. This is not an efficient way to eat sugar or to accumulate carats.