ConverterHub

Grains to Grams Converter

Enter a value in grains to convert it to grams, milligrams.

Result

11.3398 g
11,339.81 mg

How it is calculated

The conversion is one multiplication, because the grain is defined exactly in metric terms: grams = grains × 0.06479891 and milligrams = grains × 64.79891. grains is the number of grains (decimals allowed). Grams are shown to four decimals and milligrams to two, so the small values typical of this unit are not rounded away. The same number of grains applies to the avoirdupois grain and the troy grain, which are identical, so no choice between systems is needed. Pharmacy and precision-reloading figures use the same unit, but this tool only converts the number you enter; it does not know what is being weighed. To go the other way, divide grams by 0.06479891, or multiply by about 15.4324.

Worked example

A 175-grain bullet. Grams: 175 × 0.06479891 = 11.3398 g, shown as 11.3398 g. Milligrams: 175 × 64.79891 = 11,339.81 mg. So the bullet weighs about 11.34 grams, or about 0.4 of an ounce. A single grain on its own is 0.0648 g, or 64.80 mg.

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Common mistakes

  • Mixing up the grain with the carat. A carat is 200 mg, about three times as heavy as one grain (64.79891 mg), so the two cannot be swapped when weighing gems.
  • Treating the grain as a measure of volume or of count (such as grains of rice). It is a mass unit.
  • Assuming a US and a UK grain differ. They do not; the unit is the same in avoirdupois, troy and apothecary systems.
  • Reading the result in milligrams as grams when copying, since grams and milligrams are both shown. Check the unit label: 11,339.81 mg is 11.34 g, not 11,339.81 g.
  • Rounding grams to one or two decimals when reloading. Four decimals is the displayed precision for a reason: powder charges are weighed to a fraction of a grain.

About this calculator

The grain is one of the oldest units of mass still in everyday use, historically based on the weight of a single grain of barley, and standardized today at exactly 1 grain = 64.79891 milligrams = 0.06479891 grams (so roughly 15.43 grains make one gram). It's the smallest unit in both the avoirdupois and troy weight systems, which is precisely why it survives where other imperial units have faded.

Ammunition reloaders measure bullet and gunpowder charge weights in grains because a gram or ounce would be far too coarse for the precision needed, archers spec arrow and field-point weight in grains for consistent flight characteristics, and pharmacists working from older apothecary-system prescriptions and jewelers weighing gemstones still encounter the unit today.

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