How many grains are in one carat?

One metric carat equals exactly 3.08647 grains. This is derived from 1 carat = 200 milligrams and 1 grain = 64.79891 milligrams, giving 200 / 64.79891 ≈ 3.08647.

Is this the metric carat or the historical carat?

This tool uses the modern metric carat (200 mg), which has been the international standard since 1907. Historical carats varied by region and were slightly different in weight.

What is a grain in weight?

A grain (gr) is 64.79891 milligrams, or approximately 1/7000 of a pound avoirdupois. It is commonly used in ballistics for bullet and powder weights, and in pharmacology for drug dosages.

Can I convert grains back to carats?

Yes. Use the swap button to reverse the conversion. Divide any grain value by 3.08647 to get carats, or multiply carats by 3.08647 to get grains.

How precise is this conversion?

The conversion uses the exact factor 3.086471669... derived from the SI definitions of the metric carat and the grain. Results are displayed to 6 decimal places.

Carats to Grains Converter

Name: Carats to Grains Converter
Availability: InStock
Author: Nham Vu

Enter a weight in carats and instantly see the equivalent in grains (1 ct = 3.08647 gr).

Enter Weight

Weight in Carats (ct)

Weight in Grains (gr)

Conversion Reference

Carats (ct)	Grains (gr)

Formula

grains = carats × 3.086471670

Derived from: 1 ct = 200 mg; 1 gr = 64.79891 mg → 200 / 64.79891 ≈ 3.08647

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Summary

Enter a weight in carats and instantly see the equivalent in grains (1 ct = 3.08647 gr).

How it works

Enter the weight in carats in the input field.
The converter multiplies your value by 3.08647 (the exact conversion factor).
The result in grains appears instantly below the input.
Use the swap button to convert grains back to carats.
Copy either value to your clipboard with one click.

Use cases

Convert gemstone weights from carats to grains for historical reference.
Compare precious metal weights across different measurement systems.
Use in ballistics or reloading contexts where grain is the standard.
Academic and research conversion between metric and traditional units.
Verify weights when dealing with antique scales calibrated in grains.
Cross-reference gem lab reports that use mixed unit systems.

Frequently Asked Questions

Last updated: 2026-06-09 · Reviewed by Nham Vu