About the Grains to Grams
This grains to grams converter changes a weight in grains (gr) into grams and milligrams, and converts grams back to grains in the second field. The grain is a tiny unit — one grain is exactly 64.79891 milligrams — that is still used every day for bullet and powder weights, arrow points and inserts, and some medicines such as aspirin.
Handloaders and shooters use it to compare bullet weights listed in grains with European data in grams; archers use it to total arrow weight; pharmacists and patients use it to read older prescriptions and apothecary labels. The table lists typical grain weights from a 5-grain aspirin to a full pound (7,000 grains).
The grain is identical in the avoirdupois, troy and apothecaries' systems, so no matter which system your source uses the conversion is the same. This tool converts units only — always follow the dosage on a medicine's label or from your pharmacist, and published load data for ammunition.
With the default inputs, the grams is 3.5639 g. Change any value above to recalculate instantly.
How to use the grains to grams
- 1Enter the weight in grains (for example a bullet weight or tablet strength).
- 2Read the grams and milligrams, plus ounces.
- 3To convert the other way, type a weight in grams in the second field.
- 4Use the table for common bullet, arrow and tablet weights.
Formula and method
Since the 1959 international yard and pound agreement, the pound is exactly 0.45359237 kg and is divided into exactly 7,000 grains. So one grain is 453.59237 g ÷ 7,000 = 0.06479891 g (64.79891 mg). Multiply grains by 0.06479891 to get grams, or divide grams by it to get grains.
The same grain is used in troy weight (480 grains per troy ounce) and avoirdupois weight (437.5 grains per ounce), which is how the ounce outputs are calculated.
- gr
- Grains (not to be confused with grams, g)
- g
- Grams
Worked examples
55-grain .223 bullet
55 × 0.06479891 = 3.564 g. One gram, in the reverse field, is 1 ÷ 0.06479891 = 15.43 grains.
5-grain aspirin tablet
5 × 64.79891 mg = 324 mg, which is why a "5 grain" aspirin is labelled 325 mg. Half a gram is 0.5 ÷ 0.06479891 = 7.72 grains.
A pound in grains
7,000 grains × 0.06479891 = 453.59 g, exactly one avoirdupois pound (16 oz). One ounce of 28.3495 g is 437.5 grains.
Frequently asked questions
How many grams are in a grain?+
One grain equals exactly 0.06479891 grams, or 64.79891 milligrams. It is a very small unit — about 15.4 grains make one gram.
How many grains are in a gram?+
One gram is about 15.4324 grains. Divide the grams by 0.06479891 to get the exact number of grains.
Why are bullets measured in grains?+
The grain is a traditional English unit that is precise enough for small projectiles and powder charges. US and UK makers kept it, so bullet weights like 55 gr or 150 gr are standard.
Is a grain the same as a gram?+
No. A gram is about 15.4 times heavier than a grain. The abbreviations are easy to confuse — "gr" is grains, "g" is grams — which matters for medicine and reloading.
How many grains are in an ounce?+
An avoirdupois ounce (used for food and general weight) is 437.5 grains; a troy ounce (used for precious metals) is 480 grains. A pound is 7,000 grains.