How many milligrams is 1 carat?

Exactly 200 milligrams. The metric carat (ct) has been defined as 0.2 grams (200 mg) since the 1907 Fourth General Conference on Weights and Measures.

Is a jewelry carat the same as a gold karat?

No. A carat (ct) is a unit of mass equal to 200 mg, used for gemstones. A karat (kt or k) is a unit of gold purity (24 karat = pure gold). They are spelled and used differently.

Why is the carat used for diamonds instead of grams?

Carats provide finer resolution for small gemstones. A 0.50 ct diamond weighs 0.1 g — expressing that as 100 mg or 0.5 ct is more precise and industry-standard than a fractional gram.

Can I convert milligrams back to carats with this tool?

Yes. Enter a value in the milligrams field and the tool calculates carats automatically (divide by 200).

Is the conversion exact or rounded?

The conversion is mathematically exact: 1 ct = 200 mg. The tool displays up to 6 decimal places so you can work with very small or very large weights without loss of precision.

Carats to Milligrams Converter

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

Enter Weight

Carats (ct)

Milligrams (mg)

1 carat = 200 milligrams · exact by definition

Result

Enter a value above to see the conversion.

Quick Reference

Carats (ct)	Milligrams (mg)

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Summary

The carats to milligrams converter lets you instantly translate any weight in carats (ct) to milligrams (mg). One metric carat is defined as exactly 200 milligrams, a standard adopted internationally in 1907 for weighing gemstones and precious metals. Whether you are evaluating a diamond, a sapphire, or a gold alloy, this tool delivers the precise milligram value with no rounding errors.

How it works

Enter a weight value in the carats input field.
The tool multiplies your value by 200 (the exact carat-to-milligram factor).
The milligram result appears immediately below.
You can also enter milligrams to convert back to carats.
Click "Copy Result" to copy the output value to your clipboard.

Use cases

Verify diamond or gemstone weight when switching between lab reports.
Cross-check jewelry specifications listed in different unit systems.
Convert precious-metal alloy batch weights for a manufacturing workflow.
Double-check a gemologist's appraisal figure against a milligram scale reading.
Teach or study the metric carat definition in a classroom setting.
Build a quick sanity-check into a gem-trading spreadsheet.

Frequently Asked Questions

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