How many milligrams are in one carat?

Exactly 200 milligrams. The carat was internationally standardized in 1907 at exactly 200 milligrams (0.2 grams). This clean definition makes carat-to-milligram conversion trivially simple: multiply carats by 200 to get milligrams, or divide milligrams by 200 to get carats.

Why was the carat standardized at 200 milligrams?

The traditional carat varied by region, ranging from about 189 to 215 milligrams. When the metric carat was standardized in 1907, 200 milligrams was chosen because it was close to the historical average and produced a clean metric number. The round figure eliminated conversion complexity and regional discrepancies simultaneously.

Is this conversion used in the jewelry industry daily?

Yes, constantly. Diamond grading laboratories weigh stones on precision balances calibrated in milligrams, then report weights in carats. A GIA (Gemological Institute of America) certificate lists diamond weight to the hundredth of a carat, which corresponds to 2-milligram precision. The milligram is the measurement; the carat is the commercial language.

Milligrams to Carats (mg to ct) Converter

1 mg = 0.005 ct

1 Milligram equals 0.005 Carats (1 mg = 0.005 ct). Convert Milligrams to Carats with formula, table, and examples.

One milligram equals exactly 0.005 carats. Both units are metric, making this a clean decimal conversion: since one carat is defined as exactly 200 milligrams, one milligram is exactly one two-hundredth of a carat. This conversion is essential in gemology, where small diamonds and precious stones are measured in both milligrams and carats.

How to Convert Milligrams to Carats

ct = mg ÷ 200

Divide the value in Milligrams by 200

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

Common Milligrams to Carats Conversions

Milligrams (mg)	Carats (ct)	Status
1 mg	0.005 ct
5 mg	0.025 ct
10 mg	0.05 ct
25 mg	0.125 ct
50 mg	0.25 ct
100 mg	0.5 ct
200 mg	1 ct
250 mg	1.25 ct
500 mg	2.5 ct
1,000 mg	5 ct
2,000 mg	10 ct
5,000 mg	25 ct
10,000 mg	50 ct
50,000 mg	250 ct
100,000 mg	500 ct

Good to Know About Milligrams to Carats Conversion

The milligram-to-carat conversion is performed thousands of times daily in the world's diamond trading centers - Antwerp, Mumbai, Tel Aviv, and New York. When a rough diamond arrives at a cutting facility, it is weighed in milligrams on a laboratory balance. The cutter plans their cuts to maximize carat weight, knowing that each milligram saved translates to 0.005 carats of saleable diamond. At $5,000 per carat for a high-quality stone, every milligram is worth $25. The milligram-to-carat factor of 0.005 is literally worth money.

Milligrams to Carats: What You Need to Know

Gemologists and diamond graders regularly convert between milligrams and carats. Laboratory scales weigh stones in milligrams for precision, then the weight is expressed in carats for commercial pricing. A diamond weighing 100 milligrams on a lab scale is listed as 0.5 carats in a jewelry catalog. This conversion happens thousands of times daily in the global gem trade.

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 →

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 →

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

Milligrams to Carats FAQ

Exactly 200 milligrams. The carat was internationally standardized in 1907 at exactly 200 milligrams (0.2 grams). This clean definition makes carat-to-milligram conversion trivially simple: multiply carats by 200 to get milligrams, or divide milligrams by 200 to get carats.
The traditional carat varied by region, ranging from about 189 to 215 milligrams. When the metric carat was standardized in 1907, 200 milligrams was chosen because it was close to the historical average and produced a clean metric number. The round figure eliminated conversion complexity and regional discrepancies simultaneously.
Yes, constantly. Diamond grading laboratories weigh stones on precision balances calibrated in milligrams, then report weights in carats. A GIA (Gemological Institute of America) certificate lists diamond weight to the hundredth of a carat, which corresponds to 2-milligram precision. The milligram is the measurement; the carat is the commercial language.

Non-Frequently Asked Questions About Milligrams to Carats

Questions nobody should ask - but someone did.

200 milligrams is exactly 1 carat - a significant and commercially valuable diamond. Whether it is 'impressive' depends on who you ask, but a 1-carat diamond typically costs $4,000 to $20,000 depending on cut, clarity, and color. Expressing it as '200 milligrams' makes it sound like a pharmaceutical dose rather than a luxury purchase. Stick with carats for romantic purposes.
Most kitchen scales resolve to 1 gram (1,000 milligrams). A 0.5-carat diamond weighs 100 milligrams - ten times below the kitchen scale's resolution. You would need a jeweler's scale (resolves to 1 mg) or a laboratory balance (resolves to 0.1 mg) to weigh diamonds meaningfully. The kitchen scale would simply read zero.
Yes, if you work with gemstones. Alternatively, remember '200 milligrams per carat' or 'divide milligrams by 200.' These three formulations are all equivalent and cover every practical milligram-to-carat scenario. The factor of 200 is one of the few clean conversion numbers in gemology, and jewelers who internalize it can estimate carat weight from milligram readings instantly.