Grain
Also: gr, Troy Grain
The grain (abbreviation: gr) is the smallest unit of the troy weight system and equals exactly 0.06479891 grams.
The grain (abbreviation: gr) is the smallest unit of the troy weight system and therefore one of the oldest units of measurement still in use in the precious metals trade. Historically, the grain was derived from the average weight of a wheat grain — a reference that was widespread across many medieval trading cultures. Since international standardisation, the value has been fixed precisely: 1 grain = 0.06479891 grams.
Position in the Troy System
The troy weight system — the basis of all precious metal weights worldwide — is structured hierarchically:
| Unit | Grains | Grams |
|---|---|---|
| 1 Grain | 1 gr | 0.064799 g |
| 1 Pennyweight | 24 gr | 1.555174 g |
| 1 Troy Ounce (fine ounce) | 480 gr | 31.103477 g |
| 1 Troy Pound | 5,760 gr | 373.241722 g |
The grain is identical in both the troy and avoirdupois systems — the only value shared by both. Nevertheless, the avoirdupois ounce (437.5 gr) differs considerably from the troy ounce (480 gr), which can lead to confusion in everyday trade.
Conversion
1 troy ounce = 480 grains = 31.1035 g
1 grain = 1/480 troy ounce ≈ 0.002083 troy oz
Use the unit converter to quickly convert grains into grams, pennyweights, or troy ounces.
Practical Significance Today
In the modern precious metals trade, the grain plays a role primarily in the following areas:
- Coin specifications: US coinage laws (e.g. the Coinage Act) define the weights of historical coins in grains.
- Firearms: Powder and projectile weights are still expressed in grains in the United States today.
- Pharmacy (historical): Apothecary weights used the grain as a base unit; today replaced by the metric system.
- Jewellery and dental alloys: Occasionally encountered when describing historical dental gold alloys.
For the melt value calculator or the gold calculator, grams and troy ounces are the relevant input units; the grain serves there as an intermediate unit during conversion.
Distinction: Grain vs. Carat vs. Gram
The grain must not be confused with the carat as a diamond weight (1 ct = 0.2 g) or the carat as a gold fineness designation (e.g. 18 carat = 750 ‰) — entirely different concepts that merely sound similar.
In Brief
The grain is a precisely defined, immutable unit (0.06479891 g) with a long history. Anyone breaking troy ounces down into their smallest sub-units or looking up historical coin weights will find the grain indispensable.