Carats To Grains Converter

Convert carats to grains using a precise formula based on standard mass definitions.

3.09

How To Convert Carats to Grains

Formula: grains = carats × 3.08647167

Example: Convert 3.5 carats to grains, 3.5 × 3.08647167 = 10.80265085 grains.

To convert by hand, you only need one number, 3.08647167. Multiply your carat value by this number. If you have a calculator, it takes one step. If you are estimating, you can round the factor to 3.09 for a quick answer.

Quick Answer

1 carat = 3.08647167 grains

2 carats = 6.17294334 grains
5 carats = 15.43235835 grains
10 carats = 30.86471670 grains

Conversion Formula

grains = carats × 3.08647167

grains = carats × (200 / 64.79891)

This means each carat is a little more than 3 grains. The second line shows where the factor comes from, 1 carat is exactly 200 milligrams, and 1 grain is exactly 64.79891 milligrams. Dividing 200 by 64.79891 gives 3.08647167.

Write your weight in carats.
Multiply by 3.08647167.
The result is the weight in grains.

Carat

A carat is a unit of mass used for gemstones and pearls. Its symbol is ct, and 1 carat is exactly 0.2 grams.

The carat name comes from carob seeds, once used as small reference weights in trade. In 1907, it was standardized internationally to the exact value used today.

Weighing diamonds, rubies, sapphires, and other gemstones
Pearl grading and jewelry sales listings
Stone matching for earrings and pairs
Lab reports from gemological labs
Insurance and appraisal documents for jewelry

Grain

A grain is a unit of mass used mainly in firearms, archery, and some older weighing systems. Its symbol is gr, and 1 grain is exactly 64.79891 milligrams.

Historically, the grain was based on the mass of a grain of cereal. Today it is fixed by the international pound, defined as 453.59237 grams, with exactly 7000 grains in one pound.

Bullet and powder weights in shooting and reloading
Arrow and bolt weights in archery
Small mass measurements in older technical references
Comparing very small weights without using decimals in grams

Is this Conversion of Carats To Grains Accurate?

Yes. This conversion is based on fixed, internationally used definitions. The carat is defined exactly as 200 milligrams, and the grain is defined exactly as 64.79891 milligrams (derived from the international pound). Because both units have exact definitions, the factor 1 carat = 3.08647167 grains is reliable for jewelry work, documentation, and technical comparison. For more details about how we choose and verify standards, read our accuracy standards.

Real Life Examples

Here are practical situations where converting carats to grains helps, especially when two industries use different units.

Diamond listing to a grains based spec sheet: A jeweler lists a diamond as 1.25 ct. In grains that is 1.25 × 3.08647167 = 3.85808959 gr, useful when a legacy system stores small masses in grains.
Matching a pair of stones: Two stones are 0.75 ct each. Each stone is 0.75 × 3.08647167 = 2.31485375 gr, making it easier to compare differences in a grains only tool.
Appraisal note with alternate units: An appraisal mentions a center stone of 5 ct. Converting gives 5 × 3.08647167 = 15.43235835 gr, which can be added to older inventory records.
Bulk parcel weighing in carats: A parcel totals 20 ct. In grains it is 20 × 3.08647167 = 61.72943340 gr, helpful when a report template expects grains.
Small stone comparison: A 0.50 ct stone equals 0.50 × 3.08647167 = 1.54323584 gr, giving a quick sense of mass in a smaller unit.
Gem lab report check: A lab report shows 2.5 ct. Converting gives 7.71617918 gr, useful for cross checking entries when different units appear across documents.
Inventory rounding decisions: If an item is 7 ct, it is 7 × 3.08647167 = 21.60530169 gr. This can help decide how many decimal places you need when storing or printing weights.

Quick Tips

Remember the key factor, 1 ct ≈ 3.09 gr for fast estimates.
For more accuracy, use 3.08647167 as the multiplier.
To double check, 2 ct should be about 6.17 gr, which matches the exact value.
If your answer seems too small, you may have divided instead of multiplied.
Keep unit symbols clear, ct for carat, gr for grain.
When reporting, keep a consistent rounding style, for example 8 decimal places.

Table Overview

Carats	Grains
0.25 carats	0.77161792 grains
0.5 carats	1.54323584 grains
0.75 carats	2.31485375 grains
1 carat	3.08647167 grains
1.25 carats	3.85808959 grains
1.5 carats	4.62970751 grains
2 carats	6.17294334 grains
2.5 carats	7.71617918 grains
3 carats	9.25941501 grains
3.5 carats	10.80265085 grains
4 carats	12.34588668 grains
5 carats	15.43235835 grains
7 carats	21.60530169 grains
10 carats	30.86471670 grains
20 carats	61.72943340 grains

FAQs

How many grains are in 1 carat?

There are 3.08647167 grains in 1 carat.

How do I convert carats to grains quickly?

Multiply carats by 3.08647167. For a quick estimate, use 3.09.

Is a carat a unit of weight or size?

A carat is a unit of mass. Stone size can look different even at the same carat weight.

Is carat the same as karat?

No. Carat (ct) measures gemstone mass. Karat (K) measures gold purity.

Why is the grains value so exact?

Because 1 carat is exactly 200 mg, and 1 grain is exactly 64.79891 mg, so the conversion factor is based on fixed definitions.

What symbol should I use for grains?

The common symbol is gr. Do not confuse it with g, which means gram.

Should I round the result?

For jewelry listings, rounding is common. For lab work or documentation, keep more decimals, like 6 to 8 decimal places.