Back Granu (unidá) AST Гран Byelorussian Гран BE-X-OLD Гран Bulgarian Greunenn (unanenn) Breton Gra (unitat de massa) Catalan Grain Czech Gran (vægtenhed) Danish Gran (Einheit) German Grano (unidad de masa) Spanish

Grain (unit)

For other uses, see Grain (disambiguation).
Grain
The small golden disc close to the 5 cm marker is a piece of pure gold weighing one grain. Shown for comparison is a tape measure and coins of major world currencies.
General information
Unit systemTroy weight, avoirdupois weight, apothecaries' weight
Unit ofMass
Symbolgr
Conversions
1 gr in ...... is equal to ...
   Troy   1⁄5760 troy pound
   Avoirdupois   1⁄7000 pound
   Apothecaries'   1⁄5760 apothecaries' pound
   SI units   64.79891 mg

A grain is a unit of measurement of mass, and in the troy weight, avoirdupois, and apothecaries' systems, equal to exactly 64.79891 milligrams. It is nominally based upon the mass of a single ideal seed of a cereal. From the Bronze Age into the Renaissance, the average masses of wheat and barley grains were part of the legal definitions of units of mass. Expressions such as "thirty-two grains of wheat, taken from the middle of the ear" appear to have been ritualistic formulas.[1]: 27 [2] Another source states that it was defined such that 252.458 units would balance 1 cubic inch (16 cm3) of distilled water at an ambient air-water pressure and temperature of 30 inches of mercury (100 kPa) and 62 °F (17 °C) respectively.[3] Another book states that Captain Henry Kater, of the British Standards Commission, arrived at this value experimentally.[4]

The grain was the legal foundation of traditional English weight systems,[5] and is the only unit that is equal throughout the troy, avoirdupois, and apothecaries' systems of mass.[6]: C-6  The unit was based on the weight of a single grain of barley which was equal to about +4⁄3 the weight of a single grain of wheat.[5][7]: 95  The fundamental unit of the pre-1527 English weight system, known as Tower weights, was based on the wheat grain.[8] The tower "wheat" grain was defined as exactly +45⁄64 (≈+3⁄4) of the troy "barley" grain.[1]: 74 

Since the implementation of the international yard and pound agreement of 1 July 1959, the grain or troy grain (symbol: gr) measure has been defined in terms of units of mass in the International System of Units as precisely 64.79891 milligrams.[6]: C-19 [9] One gram is thus approximately equivalent to 15.43236 grains.[6]: C-13  The unit formerly used by jewellers to measure pearls, diamonds, and other precious stones, called the jeweller's grain or pearl grain, is equal to 1⁄4 carat (50 mg; 0.77 gr).[5] The grain was also the name of a traditional French unit equal to 53.115 mg.[5]

In both British Imperial units and United States customary units, there are precisely 7,000 grains per avoirdupois pound, and 5,760 grains per troy pound or apothecaries' pound.[6]: C-6–C-7  It is obsolete in the United Kingdom and, like most other non-SI units, it has no basis in law and cannot be used in commerce.[10]

  1. ^ a b McDonald, Daniel McLean; Scarre, Christopher (1992). The origins of metrology: collected papers of Dr. Daniel McLean McDonald. McDonald Institute for Archaeological Research. ISBN 9780951942000. Retrieved 15 September 2012.
  2. ^ Connor, R. D. (1987). The weights and measures of England. H.M.S.O. p. 124. ISBN 978-0-11-290435-9. Retrieved 2 February 2012.
  3. ^ Alexander, John Henry (1850). "Weight (United States of America)". Universal Dictionary of Weights and Measures, Ancient and Modern: Reduced to the Standards of the United States of America. Baltimore. p. 132. Retrieved 2016-09-23.{{cite encyclopedia}}: CS1 maint: location missing publisher (link)
  4. ^ Oldberg, Oscar (1885). A Manual of Weights, Measures, and Specific Gravity. Chicago: self-published. p. 87. Retrieved 2016-09-24.
  5. ^ a b c d Rowlett, Russ (13 September 2001). "Grain". How Many? A Dictionary of Units of Measurement. Chapel Hill, North Carolina: University of North Carolina at Chapel Hill. Retrieved 13 October 2024 – via iBiblio.org.
  6. ^ a b c d Crown, Linda D.; Butcher, Tina G.; Cook, Steven E.; Harshman, Richard A., eds. (October 26, 2011). "Appendix C – General Tables of Units of Measurement" (PDF). Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices (NIST HB 44) (Standard). Gaithersburg, Maryland: National Institute of Standards and Technology (published 2012). Retrieved 2024-10-13.
  7. ^ Cite error: The named reference Ridgeway1889 was invoked but never defined (see the help page).
  8. ^ Zupko, Ronald Edward (1977). British weights & measures: a history from antiquity to the sixteenth century. University of Wisconsin Press. p. 11. ISBN 9780299073404. Retrieved 18 December 2011.
  9. ^ Judson, Lewis V. (March 1976) [October 1963]. "8. Refinement of values for the yard and pound". Weights and Measures Standards of the United States: A brief history (PDF). NBS Special Publication. Vol. 447. Washington, D.C.: U.S. Department of Commerce, National Bureau of Standards. p. 20. OCLC 610190761. Archived from the original (PDF) on 3 June 2011. Retrieved 30 June 2012.
  10. ^ "Weights and Measures: the Law". UK Government. Retrieved 2021-11-11.

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