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What is a grain?

Used in firearms (bullet weight) and some pharmaceutical dosing

Definition

The grain equals 64.79891 milligrams exactly, one of the oldest units of mass. Originally defined as the weight of a single grain of barley. Today used almost exclusively in firearms (bullet and gunpowder weights) and pharmaceuticals.

Common uses

  • Bullet and gunpowder mass in ballistics
  • Older pharmaceutical dosing in Anglo-Saxon countries
  • Arrow shaft and archery equipment weights

🌍 Real-world scale

A 9 mm bullet typically weighs 115–124 grains (7.45–8.03 g). Aspirin grain dosing: "5 grain aspirin" = 325 mg.

Convert from grains

11 conversions
Grain to Kilogram1 gr = 6.4799e-5 kgGrain to Gram1 gr = 0.0648 gGrain to Milligram1 gr = 64.7989 mgGrain to Microgram1 gr = 64,798.91 µgGrain to Pound1 gr = 0.0001429 lbGrain to Ounce1 gr = 0.002286 ozGrain to Metric Ton1 gr = 6.4799e-8 tGrain to US Ton1 gr = 7.1429e-8 ton (US)Grain to UK Ton1 gr = 6.3776e-8 ton (UK)Grain to Stone1 gr = 1.0204e-5 stGrain to Carat1 gr = 0.324 ct

Convert to grains

11 conversions
Kilogram to Grain1 kg = 15,432.36 grGram to Grain1 g = 15.4324 grMilligram to Grain1 mg = 0.01543 grMicrogram to Grain1 µg = 1.5432e-5 grPound to Grain1 lb = 7,000 grOunce to Grain1 oz = 437.5 grMetric Ton to Grain1 t = 15,432,358.35 grUS Ton to Grain1 ton (US) = 14,000,000 grUK Ton to Grain1 ton (UK) = 15,680,000 grStone to Grain1 st = 98,000 grCarat to Grain1 ct = 3.08647 gr

Tips

  • 1 grain = 64.79891 mg exactly. 7000 grains = 1 pound.
  • Ballistics is one of the few modern contexts where grains are essential.
  • Some older pharmacology dosing survives in grain units — 5 gr ≈ 325 mg.

Common mistakes

  • Confusing the grain (mass) with the troy grain in older precious-metal contexts — they are identical (64.8 mg).
  • Assuming "grain" refers to an amount of cereal — in firearms it is always a weight.
  • Reading "5 gr" as 5 grams — it is 5 grains (324 mg).

FAQ about the grain

What is a grain?
The grain equals 64.79891 milligrams exactly, one of the oldest units of mass. Originally defined as the weight of a single grain of barley. Today used almost exclusively in firearms (bullet and gunpowder weights) and pharmaceuticals.
Where is the grain used?
The grain is commonly used for: Bullet and gunpowder mass in ballistics; Older pharmaceutical dosing in Anglo-Saxon countries; Arrow shaft and archery equipment weights.
What is an example of a grain in real life?
A 9 mm bullet typically weighs 115–124 grains (7.45–8.03 g). Aspirin grain dosing: "5 grain aspirin" = 325 mg.
What category does the grain belong to?
The grain is a unit of weight, part of the 12-unit weight category on UnitConv.
How accurate are grain conversions?
All conversion factors follow NIST and BIPM international standards to 8 significant figures — the highest practical accuracy.
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