The dry gallon, also known as the corn gallon or grain gallon, is a historic British

dry measure Dry measures are units of volume to measure bulk commodities that are not fluids and that were typically shipped and sold in standardized containers such as barrels. They have largely been replaced by the units used for measuring volumes in the met ...

of volume that was used to measure grain and other dry commodities and whose earliest recorded official definition, in 1303, was the volume of of wheat. It is not used in the US customary system – though it implicitly exists since the US dry measures of

bushel A bushel (abbreviation: bsh. or bu.) is an imperial and US customary unit of volume based upon an earlier measure of dry capacity. The old bushel is equal to 2 kennings (obsolete), 4 pecks, or 8 dry gallons, and was used mostly for agri ...

peck A peck is an imperial and United States customary unit of dry volume, equivalent to 2 dry gallons or 8 dry quarts or 16 dry pints. An imperial peck is equivalent to 9.09 liters and a US customary peck is equivalent to 8.81 liters. Two pecks m ...

quart The quart (symbol: qt) is an English unit of volume equal to a quarter gallon. Three kinds of quarts are currently used: the liquid quart and dry quart of the US customary system and the of the British imperial system. All are roughly e ...

, and

pint The pint (, ; symbol pt, sometimes abbreviated as ''p'') is a unit of volume or capacity in both the imperial and United States customary measurement systems. In both of those systems it is traditionally one eighth of a gallon. The British imp ...

are still used – and is not included in the

National Institute of Standards and Technology The National Institute of Standards and Technology (NIST) is an agency of the United States Department of Commerce whose mission is to promote American innovation and industrial competitiveness. NIST's activities are organized into Outline of p ...

handbook that many US states recognize as the authority on measurement law.101st Conference on Weights and Measures 2016. (2017)
''Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices''

. p. C-6, C-11, C-16.''Summary of State Laws and Regulations in Weights and Measures''
. (2005)

. The US fluid gallon is about 14.1% smaller than the dry gallon, while the Imperial fluid gallon is about 3.2% larger. Its implicit value in the US system was originally one eighth of the Winchester bushel, which was a cylindrical measure of in diameter and in depth, which made the dry gallon an

irrational number In mathematics, the irrational numbers (from in- prefix assimilated to ir- (negative prefix, privative) + rational) are all the real numbers that are not rational numbers. That is, irrational numbers cannot be expressed as the ratio of two inte ...

in cubic inches whose value to seven significant digits was , or exact cubic inches. Since the bushel was later defined to be exactly 2150.42 cubic inches, this figure became the exact value for the dry gallon ( gives exactly ).

References

Units of volume {{measurement-stub