Pounds to Grains (lb to gr)

1 pound equals 7,000 grains exactly.

1 pound = 7,000 grains

How to convert pounds to grains

To convert pounds to grains, multiply the number of pounds by 7,000. This factor is exact. To go the other way, multiply grains by 0.0001428571429 (rounded).

grains = pounds × 7,000

Example: 10 pounds = 70,000 grains.

About these units

Pound (lb)

US & ImperialCurrent unit

Exactly 0.45359237 kg, divided into 16 ounces. The standard unit of weight in the US and common in the UK.

Why is pound abbreviated lb? The answer is Roman. The English word comes from the Latin libra pondo, roughly the weight measured in libra, and the symbol keeps the first word. The Roman libra was divided into 12 unciae. The avoirdupois pound of 16 ounces came into general use around 1300 and was initially equal to 6,992 troy grains; under Elizabeth I it was redefined as 7,000 grains. The UK's Weights and Measures Act 1878 set the imperial standard pound as a platinum cylinder, and the troy pound was abolished for trade the following year.

Today the pound is defined from the kilogram. The International Yard and Pound Agreement of 1959 fixed it at exactly 0.45359237 kg, and the UK's Weights and Measures Act 1963 wrote the same figure into law. Pounds remain the everyday unit for body weight, groceries and shipping in the United States and are widely used in the UK. The word also survives in odd places: a six-pounder cannon was named for the weight of its shot, not its own.

1 pound = 0.45359237 kilograms (exactly).

Sources: Wikipedia: Pound (mass); 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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