Ounces to Grains (oz to gr)

1 ounce equals 437.5 grains exactly.

1 ounce = 437.5 grains

How to convert ounces to grains

To convert ounces to grains, multiply the number of ounces by 437.5. This factor is exact. To go the other way, multiply grains by 0.002285714286 (rounded).

grains = ounces × 437.5

Example: 10 ounces = 4,375 grains.

About these units

Ounce (oz)

US & ImperialCurrent unit

One sixteenth of a pound, exactly 28.349523125 g. Used for food, mail and consumer goods in the US and UK.

A twelfth part is what ounce originally meant. It comes from the Roman uncia, one twelfth of the Roman pound, a word that also gave English the inch. The abbreviation oz does not come from English at all but from the Italian onza or oncia. Over the centuries many regions and trades used different ounces: the English Tower ounce of 29.16 g was abolished by Henry VIII in 1527, and the Dutch ons was redefined as exactly 100 g in 1820.

The avoirdupois ounce used for everyday goods is one sixteenth of a pound, exactly 28.349523125 g or 437.5 grains, the standard in the US and under the UK imperial system. It is not the same as the troy ounce for precious metals, and neither is the fluid ounce, which measures volume. Ounces still describe portions such as steaks and burgers, and they show up in unexpected places: fabric is graded by weight per area, so a 16 oz denim is a heavy cloth, and the copper on a circuit board is specified in ounces, where 1 oz is roughly 34.7 micrometres thick.

1 ounce = 0.02834952313 kilograms (approximately).

Sources: Wikipedia: Ounce; NIST Guide to the SI, Appendix B.8 (mass conversions)

Grain (gr)

US & ImperialTraditional unit (still used in some regions)

Exactly 64.79891 mg, based on the weight of a grain of barley. Still used for the weight of bullets, arrows and some medicines.

Barley and wheat seeds served as the earliest common weights in the Mediterranean, because a dry seed is small and fairly consistent. Medieval English law tied weights to the average mass of such grains, and the name grain stuck even after the link to actual cereal faded. The unit is exactly 64.79891 milligrams, fixed by the 1959 international yard and pound agreement, and NIST lists the same figure of 6.479891 x 10^-5 kilogram as exact.

Grain is unusual in being identical in the troy, avoirdupois and apothecaries' systems. A troy pound has 5,760 grains and an avoirdupois pound has 7,000. Modern use is mostly in niches: bullet and propellant weights, arrow weights in archery, and water hardness expressed as grains per gallon. Older drug doses were also given this way, with a standard 325 milligram aspirin tablet equal to five grains. Jewelers once used a pearl grain, a quarter of a carat. In the United Kingdom the unit has no legal standing for trade.

1 grain = 0.00006479891 kilograms (exactly).

Sources: Wikipedia: Grain (unit); NIST SP 811 Appendix B.8 (conversion factors)

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