How many milligrams are in one carat?

Exactly 200 milligrams equal one metric carat. This is a fixed international definition (1 ct = 0.2 g = 200 mg), so the conversion is always exact with no rounding involved in the ratio itself.

Is the carat used here the same as karat for gold purity?

No. The carat (ct) used in this tool is a unit of mass equal to 200 mg, used for gemstones. The karat (k or kt) is a different term that describes gold purity on a 24-point scale and has nothing to do with mass.

How do I convert carats back to milligrams?

Multiply the carat value by 200. For example, a 0.5 ct diamond weighs 0.5 × 200 = 100 mg. You can also enter a value in the carat field on this tool to see the reverse conversion.

Why do jewelers use carats instead of grams?

The carat predates the metric system and became the global standard for gemstone trading. Gem weights are typically small fractions of a gram, so carats (and hundredths of a carat called "points") provide a more practical scale for the industry.

What is the smallest carat value I can convert?

The tool handles any positive number, including fractions. A single point (0.01 ct) equals just 2 mg. The result is displayed with up to 6 decimal places to preserve precision for very small stones.

Milligrams to Carats Converter

Enter a mass in milligrams and instantly get the equivalent weight in carats (1 ct = 200 mg).

Enter Weight in Milligrams

Milligrams (mg)

Carats (ct) — reverse input

Common Conversions

Milligrams (mg)	Carats (ct)

Formula

carats = milligrams ÷ 200

milligrams = carats × 200

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Summary

The milligram-to-carat converter lets you instantly translate any mass expressed in milligrams into the metric carat unit used by gemologists and jewelers worldwide. One metric carat is defined as exactly 200 milligrams, making the conversion a simple division by 200. Whether you are grading diamonds, evaluating colored stones, or converting lab measurements, this tool gives you a precise result in real time.

How it works

Type a milligram value into the input field.
The tool divides the value by 200 to obtain carats.
The result is shown immediately — no button press needed.
Click "Copy Result" to copy the carat value to your clipboard.
Use the quick-reference table below to look up common conversions.

Use cases

Converting gemstone weights reported in milligrams to carats for grading certificates.
Calculating carat weight from lab precision-scale readings.
Double-checking supplier invoices that list stone weight in milligrams.
Teaching jewelry students the relationship between carats and milligrams.
Quickly comparing gem weights across different unit systems.
Verifying carat claims on vintage jewelry using a milligram scale.

Frequently Asked Questions

Last updated: 2026-06-04 · Reviewed by Nham Vu