Grains to Grams Converter
| Item | Grains | Grams |
|---|---|---|
| Arrow point, target | 100 gr | 6.48 |
| Arrow point, hunting | 125 gr | 8.1 |
| 9 mm bullet, common | 115 gr | 7.45 |
| 9 mm bullet, heavy | 147 gr | 9.53 |
| .223 bullet | 55 gr | 3.56 |
| Aspirin tablet, historic | 5 gr | 0.32 |
The grain is the oldest weight unit still on working papers: defined as one barleycorn's worth, standardized at exactly 64.79891 milligrams, and untouched by every reform since - the troy and avoirdupois systems disagree about ounces but share this same grain. It survives where tradition has teeth: arrow points, bullet weights, and black-powder charges are all quoted in grains, so the conversion to grams is 0.0648 per grain.
Type either unit and the converter lands the other. The anchors: a modern arrow point runs 100-125 grains, a 9 mm bullet is typically 115-147 grains, and a 55-grain .223 round is 3.56 grams - the table carries the everyday weights so a load data sheet and a metric scale agree on the first read.
How to use
- Type the grains from a load sheet, arrow spec or powder measure - grams appear instantly.
- Or run it backwards from a metric scale reading to the grains the specification quotes.
- Check the table: arrow points cluster 75-150 grains, common bullets 55-180, and the factor never drifts.
Frequently asked questions
How many grams is 1 grain?
Exactly 0.06479891 grams - about the mass of a grain of barley, which is where the unit began. It is the oldest piece of the English weight system: the troy pound and the avoirdupois pound were both built from the same grain, which is why a troy ounce (480 grains) and an avoirdupois ounce (437.5 grains) weigh differently while both count in the same smallest unit.
Why is ammunition measured in grains?
Because the industry inherited black-powder tradition and never left: powder charges were measured in grains of powder, bullets in grains of lead, and the ratios carried over when smokeless powder arrived. A 147-grain 9 mm bullet is 9.53 grams; a 55-grain .223 is 3.56 grams. Reloading manuals, chronograph tests and ballistics tables all quote grains, so metric shooters convert rather than rewrite the canon.
Do arrows really use grains too?
Yes - arrow points, inserts and total arrow weight are quoted in grains (GPI, grains per inch, describes shaft weight). A hunting arrow builds to 350-500 grains total; target arrows run lighter. The reason is the same as bullets: ballistic tradition, plus the fact that small differences matter - twenty grains on an arrow changes trajectory noticeably, so the unit's small size is a feature.
Is a grain the same in troy and avoirdupois systems?
Yes - identical, and that is the grain's entire reason for existing. The two systems disagree about ounces and pounds (a troy pound has 12 ounces, avoirdupois 16) but both are built from the same 64.79891 mg grain, so precious metals and gunpowder could share a smallest unit while trading in different pounds. It is the system's common ancestor, preserved in every conversion.
Is the grain ever used for medicine?
Historically yes - aspirin was famously 5 grains (325 mg, which is why the standard tablet is that odd number), and very old prescriptions quote grains. Modern medicine dropped it for milligrams decades ago for safety: a unit this small invites tenfold errors. The converter still handles the old labels, because grandmothers' aspirin bottles and antique apothecary shelves keep asking.