Gallon
Encyclopedia
The gallon is a measure of volume
Volume
Volume is the quantity of three-dimensional space enclosed by some closed boundary, for example, the space that a substance or shape occupies or contains....

. Historically it has had many different definitions, but there are three definitions in current use: the imperial gallon (≈ 4.546 l) which is used in the United Kingdom and semi-officially within Canada
Canadian units
Canadian units are the traditional weights and measures used in Canada. The country has officially adopted the metric system, but still maintains legal definitions of the imperial units under Schedule II, Section 4 of the Weights and Measures Act...

, the United States liquid gallon (≈ 3.79 l) and the lesser used United States dry gallon (≈ 4.40 l). The gallon, be it the imperial or US gallon, is sometimes found in other English
English language
English is a West Germanic language that arose in the Anglo-Saxon kingdoms of England and spread into what was to become south-east Scotland under the influence of the Anglian medieval kingdom of Northumbria...

-speaking countries.

Definitions

There is one gallon defined in the imperial system and two in the U.S. customary system.

The imperial gallon
This gallon, the UK gallon, is defined as . This definition is used in some Commonwealth
Commonwealth of Nations
The Commonwealth of Nations, normally referred to as the Commonwealth and formerly known as the British Commonwealth, is an intergovernmental organisation of fifty-four independent member states...

 countries, and is based on the volume of 10 pound
Pound (mass)
The pound or pound-mass is a unit of mass used in the Imperial, United States customary and other systems of measurement...

s of water at 62 °F. (A US liquid gallon of water weighs about 8.33 pounds at the same temperature.) The imperial fluid ounce is defined as of an imperial gallon.

The US liquid gallon
This gallon is defined as 231 cubic inch
Cubic inch
The cubic inch is a unit of measurement for volume in the Imperial units and United States customary units systems. It is the volume of a cube with each of its 3 sides being one inch long....

es, and is equal to exactly or about . This is the most common definition of a gallon in the United States. The US fluid ounce
Fluid ounce
A fluid ounce is a unit of volume equal to about 28.4 mL in the imperial system or about 29.6 mL in the US system. The fluid ounce is distinct from the ounce, which measures mass...

 is defined as of a US liquid gallon.

The US dry gallon
This gallon is one-eighth of a US Winchester
Winchester measure
Winchester measure is a set of legal standards of volume defined in the city of Winchester, England during the tenth century and in use, with some modifications, until the present day.-National standard:...

bushel
Bushel
A bushel is an imperial and U.S. customary unit of dry volume, equivalent in each of these systems to 4 pecks or 8 gallons. It is used for volumes of dry commodities , most often in agriculture...

 of 2150.42 cubic inches, thus it is equal to exactly 268.8025 cubic inches or . The US dry gallon is less commonly used, and is not listed in the relevant statute, which jumps from the dry quart to the peck
Peck
A peck is an imperial and U.S. customary unit of dry volume, equivalent to 2 gallons or 8 dry quarts or 16 dry pints. Two pecks make a kenning , and four pecks make a bushel....

.

Worldwide usage of gallons

The imperial gallon is used in everyday life (and in advertising) in Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

, the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 and Ireland
Republic of Ireland
Ireland , described as the Republic of Ireland , is a sovereign state in Europe occupying approximately five-sixths of the island of the same name. Its capital is Dublin. Ireland, which had a population of 4.58 million in 2011, is a constitutional republic governed as a parliamentary democracy,...

, including alongside litres per 100 km in advertisements and other official publications for expressing fuel economy figures in miles per gallon.

The gallon was removed from the list of legally defined primary units of measure catalogued in the EU directive 80/181/EEC, for certain defined trading and official purposes only, with effect from 31 December 1994. Under the directive, for the defined purposes, the gallon could still be used - but only as a supplementary or secondary unit. One of the impacts of this directive was that the United Kingdom amended its own legislation to replace the gallon with the litre as a primary unit of measure in trade and in the conduct of public business, effective from 30 September 1995. Ireland also passed legislation in response to the EU directive with the effective date being 31 December 1993. For the purposes for which the gallon has ceased to be the legally defined primary unit, it can still be legally used in both the UK and Ireland as a supplementary unit.

The Imperial gallon is used as a unit of measure for fuel in Antigua and Barbuda
Antigua and Barbuda
Antigua and Barbuda is a twin-island nation lying between the Caribbean Sea and the Atlantic Ocean. It consists of two major inhabited islands, Antigua and Barbuda, and a number of smaller islands...

, although the government there has announced plans to convert to litres by 2015, in Belize
Belize
Belize is a constitutional monarchy and the northernmost country in Central America. Belize has a diverse society, comprising many cultures and languages. Even though Kriol and Spanish are spoken among the population, Belize is the only country in Central America where English is the official...

, name="gas-bz1"> Burma (Myanmar), name="gas-mm1"> name="gas-mm2"> name="gas-mm3"> Cayman Islands
Cayman Islands
The Cayman Islands is a British Overseas Territory and overseas territory of the European Union located in the western Caribbean Sea. The territory comprises the three islands of Grand Cayman, Cayman Brac, and Little Cayman, located south of Cuba and northwest of Jamaica...

, Grenada
Grenada
Grenada is an island country and Commonwealth Realm consisting of the island of Grenada and six smaller islands at the southern end of the Grenadines in the southeastern Caribbean Sea...

, name="gas-ab1"> and Guyana
Guyana
Guyana , officially the Co-operative Republic of Guyana, previously the colony of British Guiana, is a sovereign state on the northern coast of South America that is culturally part of the Anglophone Caribbean. Guyana was a former colony of the Dutch and of the British...

.
The United Arab Emirates
United Arab Emirates
The United Arab Emirates, abbreviated as the UAE, or shortened to "the Emirates", is a state situated in the southeast of the Arabian Peninsula in Western Asia on the Persian Gulf, bordering Oman, and Saudi Arabia, and sharing sea borders with Iraq, Kuwait, Bahrain, Qatar, and Iran.The UAE is a...

 switched from gallons to litres on 1 January 2010 and Sierra Leone switched in May 2011.

The U.S. gallon is used in the United States.

Relationship to other units

The gallons in current use are subdivided into eight pint
Pint
The pint is a unit of volume or capacity that was once used across much of Europe with values varying from state to state from less than half a litre to over one litre. Within continental Europe, the pint was replaced with the metric system during the nineteenth century...

s or four quart
Quart
The quart is a unit of volume equal to a quarter of a gallon, two pints, or four cups. Since gallons of various sizes have historically been in use, quarts of various sizes have also existed; see gallon for further discussion. Three of these kinds of quarts remain in current use, all approximately...

s. Pint
Pint
The pint is a unit of volume or capacity that was once used across much of Europe with values varying from state to state from less than half a litre to over one litre. Within continental Europe, the pint was replaced with the metric system during the nineteenth century...

s are further subdivided into fluid ounce
Fluid ounce
A fluid ounce is a unit of volume equal to about 28.4 mL in the imperial system or about 29.6 mL in the US system. The fluid ounce is distinct from the ounce, which measures mass...

s and liquid gallons are also subdivided into 32 gills
Gill (unit)
The gill is a unit of measurement for volume equal to a quarter of a pint. It is no longer in common use, except in regard to the volume of alcoholic spirits measures but it is also kept alive by the occasional reference, such as in the cumulative song, "The Barley Mow".Imperial gillUnited States...

, i.e. a quarter of a pint. The sub-units of pint
Pint
The pint is a unit of volume or capacity that was once used across much of Europe with values varying from state to state from less than half a litre to over one litre. Within continental Europe, the pint was replaced with the metric system during the nineteenth century...

 and fluid ounce
Fluid ounce
A fluid ounce is a unit of volume equal to about 28.4 mL in the imperial system or about 29.6 mL in the US system. The fluid ounce is distinct from the ounce, which measures mass...

, despite having the same name in both imperial and US units, differ in volume and are therefore not interchangeable. The principal difference is that the imperial pint
Pint
The pint is a unit of volume or capacity that was once used across much of Europe with values varying from state to state from less than half a litre to over one litre. Within continental Europe, the pint was replaced with the metric system during the nineteenth century...

 contains 20 imperial fluid ounce
Fluid ounce
A fluid ounce is a unit of volume equal to about 28.4 mL in the imperial system or about 29.6 mL in the US system. The fluid ounce is distinct from the ounce, which measures mass...

s, whereas the US pint
Pint
The pint is a unit of volume or capacity that was once used across much of Europe with values varying from state to state from less than half a litre to over one litre. Within continental Europe, the pint was replaced with the metric system during the nineteenth century...

 contains 16 US fluid ounces
Fluid Ounces
Fluid Ounces were a piano-based, power pop band from Murfreesboro, Tennessee that garnered a cult following for their critically acclaimed records, which featured a distinctive blend of hooks, varied musical styles, clever wordplay, and intricate, complex arrangements.-Inception:Seth Timbs had...

. A U.S. fluid ounce is approximately 4% bigger than an Imperial fluid ounce, and therefore they are often used interchangeably, whereas US and imperial pints and gallons are sufficiently different that they should not be used interchangeably.

History

The gallon originated as the base of systems for measuring wine
English units of wine casks
Below is a list of old English units for wine casks. In addition to the items listed below see separate articles on Gallon, Barrel, Hogshead, Firkin, Puncheon, Butt and Tun.-Rundlet:...

, and ale and beer
English units of brewery casks
Below is a list of old English units for brewery casks, used for ale and beer. In addition to the items listed below see separate articles on the individual units....

 in England. The sizes of gallon used in these two systems were different from each other: the first was based on the wine gallon (equal in size to the US gallon), and the second on either the ale gallon or the smaller imperial gallon.

By the end of the 18th century, three definitions of the gallon were in common use:
  • The corn gallon, or Winchester gallon, of about ,
  • The wine gallon
    Wine gallon
    A wine gallon is a unit of capacity that was used routinely in England as far back as the 14th century, and by statute under Queen Anne since 1707. Britain abandoned the wine gallon in 1826 when it adopted imperial units for measurement...

    , or Queen Anne's gallon, which was , and
  • The ale gallon of .


The corn or dry gallon was used in the United States until recently for grain and other dry commodities. It is one eighth of the (Winchester) bushel
Bushel
A bushel is an imperial and U.S. customary unit of dry volume, equivalent in each of these systems to 4 pecks or 8 gallons. It is used for volumes of dry commodities , most often in agriculture...

, originally a cylindrical measure of inches in diameter and 8 inches in depth. That made the dry gallon . The bushel, which like dry quart
Quart
The quart is a unit of volume equal to a quarter of a gallon, two pints, or four cups. Since gallons of various sizes have historically been in use, quarts of various sizes have also existed; see gallon for further discussion. Three of these kinds of quarts remain in current use, all approximately...

 and pint still sees some use, was later defined to be 2150.42 cubic inches exactly, making its gallon exactly .
In previous centuries, there had been a corn gallon of around 271 to 272 cubic inches.

The wine, fluid, or liquid gallon has been the standard US gallon since the early 19th century. The wine gallon, which some sources relate to the volume occupied by eight medieval merchant pounds of wine, was at one time defined as the volume of a cylinder six inches deep and seven inches in diameter, i.e. . It had been redefined during the reign of Queen Anne
Anne of Great Britain
Anne ascended the thrones of England, Scotland and Ireland on 8 March 1702. On 1 May 1707, under the Act of Union, two of her realms, England and Scotland, were united as a single sovereign state, the Kingdom of Great Britain.Anne's Catholic father, James II and VII, was deposed during the...

, in 1706, as 231 cubic inches exactly , which is the result of the earlier definition with π approximated to . Although the wine gallon had been used for centuries for import duty purposes there was no legal standard of it in the Exchequer
Exchequer
The Exchequer is a government department of the United Kingdom responsible for the management and collection of taxation and other government revenues. The historical Exchequer developed judicial roles...

 and a smaller gallon was actually in use, so this statute became necessary. It remains the US definition today.

In 1824, Britain adopted a close approximation to the ale gallon known as the imperial gallon and abolished all other gallons in favour of it. Inspired by the kilogram
Kilogram
The kilogram or kilogramme , also known as the kilo, is the base unit of mass in the International System of Units and is defined as being equal to the mass of the International Prototype Kilogram , which is almost exactly equal to the mass of one liter of water...

-litre relationship, the imperial gallon was based on the volume of 10 pounds
Pound (mass)
The pound or pound-mass is a unit of mass used in the Imperial, United States customary and other systems of measurement...

 of distilled water weighed in air with brass weights with the barometer standing at 30 inches of mercury
Inch of mercury
Inches of mercury, ' is a unit of measurement for pressure. It is still widely used for barometric pressure in weather reports, refrigeration and aviation in the United States, but is seldom used elsewhere....

 and at a temperature of . In 1963, this definition was refined as the space occupied by 10 pounds of distilled water of density weighed in air of density against weights of density . This works out at approximately . The metric definition of exactly cubic decimetres (also after the litre was redefined in 1964, ≈ ) was adopted shortly afterwards in Canada, but from 1976 the conventional value of was used in the United Kingdom until the Canadian convention was adopted in 1985.

Comparison of historic gallons

Volume Definition Inverted volume
(gallons per cubic foot)
Approx.
weight of
water (pounds
Avoirdupois
The avoirdupois system is a system of weights based on a pound of 16 ounces. It is the everyday system of weight used in the United States and is still widely used to varying degrees by many people in Canada, the United Kingdom, and some other former British colonies despite the official adoption...


per gallon
@ 62 °F)
Cylindrical approximation
(cu in
Cubic inch
The cubic inch is a unit of measurement for volume in the Imperial units and United States customary units systems. It is the volume of a cube with each of its 3 sides being one inch long....

)
(L or dm3) Diameter
(in)
Height
(in)
Relative
error (%)
216 Roman congius
Congius
In Ancient Roman measurement, congius was a liquid measure, which contained six sextarii, or the eighth-part of the amphora; that is about 3.25 litres...

8 7.8 5 11 0.01
224 ≈ 3.6707 preserved at the Guildhall, London
Guildhall, London
The Guildhall is a building in the City of London, off Gresham and Basinghall streets, in the wards of Bassishaw and Cheap. It has been used as a town hall for several hundred years, and is still the ceremonial and administrative centre of the City of London and its Corporation...

 (old UK wine gallon)
7.71 8.09 9 3.5 0.6
231 3.785411784 statute of 5th of Queen Anne (US wine gallon, standard US gallon) 7.48 8.33 7 6 0.04
264.8 ≈ 4.3393 ancient Rumford quart (1228) 6.53 9.57 7.5 6 0.1
265.5 ≈ 4.3508 Exchequer (Henry VII
Henry VII of England
Henry VII was King of England and Lord of Ireland from his seizing the crown on 22 August 1485 until his death on 21 April 1509, as the first monarch of the House of Tudor....

, 1091, with rim)
6.51 9.59 13 2 0.01
266.25 ≈ 4.3631 ancient Rumford (1228)          
268.8025 Winchester, statute 13 + 14 by William III
William III of England
William III & II was a sovereign Prince of Orange of the House of Orange-Nassau by birth. From 1672 he governed as Stadtholder William III of Orange over Holland, Zeeland, Utrecht, Guelders, and Overijssel of the Dutch Republic. From 1689 he reigned as William III over England and Ireland...

 (corn gallon, old US dry gallon)
6.43 9.71 18.5 1
271 ≈ 4.4409 Exchequer (1601, E.) (old corn gallon) 6.38 9.79 4.5 17 0.23
272 ≈ 4.4573 corn gallon (1688)          
277.18 ≈ 4.5422 statute 12 of Anne (coal gallon) = 33/32 corn gallons 6.23 10      
277.274 4.543460 Imperial Gallon (1824) as originally evaluated. 6.23 10      
(ca.) standard imperial gallon (metric) (1964 Canada gallon, 1985 UK gallon) 6.23 10      
Imperial gallon (1895) Re-determined in 1895, as defined in 1963. 6.23 10      
278 ≈ 4.5556 Exchequer (Henry VII, with copper rim) 6.21 10.04      
278.4 ≈ 4.5622 Exchequer (1601 and 1602 pints) 6.21 10.06      
280 ≈ 4.5884 Exchequer (1601 quart) 6.17 10.1      
282 ≈ 4.6212 Treasury (beer and ale gallon) 6.13 10.2      

See also

  • Comparison of the imperial and US customary measurement systems
  • English units of wine casks
    English units of wine casks
    Below is a list of old English units for wine casks. In addition to the items listed below see separate articles on Gallon, Barrel, Hogshead, Firkin, Puncheon, Butt and Tun.-Rundlet:...

  • English units of brewery casks
    English units of brewery casks
    Below is a list of old English units for brewery casks, used for ale and beer. In addition to the items listed below see separate articles on the individual units....


External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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