# Gallon

(Redirected from US gallon)

The gallon is a unit of volume in imperial units and United States customary units. Three different versions are in current use:

• the imperial gallon (imp gal), defined as 4.54609 litres, which is or was used in the United Kingdom, Ireland, Canada, Australia, New Zealand, and some Caribbean countries;
• the US gallon (US gal), defined as 3.785411784 L,[1] (231 cubic inches) which is used in the US and some Latin American and Caribbean countries; and
• the US dry gallon ("usdrygal"), defined as 18 US bushel (exactly 4.40488377086 L).
Gallon
A one-US-gallon gas can showing "U.S. Gallon" marking (for US use), imperial gallons, and litres (for Canadian use)
General information
Unit ofVolume
Symbolgal
Conversions (imperial)
1 imp gal in ...... is equal to ...
SI units   4.54609 L
US customary units   1.200950 US gal
US customary units   277.4194 in3
Conversions (US)
1 US gal in ...... is equal to ...
SI units   3.785411784 L
Imperial units   0.8326742 imp gal
Imperial units   231 in3
US dry gallon   0.859367 US dry gal

There are two pints in a quart and four quarts in a gallon. Different sizes of pints account for the different sizes of the imperial and US gallons.

The IEEE standard symbol for both US (liquid) and imperial gallon is gal,[2] not to be confused with the gal (symbol: Gal), a CGS unit of acceleration.

## Definitions

The gallon currently has one definition in the imperial system, and two definitions (liquid and dry) in the US customary system. Historically, there were many definitions and redefinitions.

### English system gallons

There were a number of systems of liquid measurements in the United Kingdom prior to the 19th century.[3]

• Winchester or corn gallon was 272 in3 (157 imp fl oz; 4,460 mL) (1697 Act 8 & 9 Will III c22)
• Henry VII (Winchester) corn gallon from 1497 onwards was 154.80 imp fl oz (4,398 mL)
• Elizabeth I corn gallon from 1601 onwards was 155.70 imp fl oz (4,424 mL)
• William III corn gallon from 1697 onwards was 156.90 imp fl oz (4,458 mL)
• Old English (Elizabethan) ale gallon was 282 in3 (163 imp fl oz; 4,620 mL) (1700 Act 11 Will III c15)
• Old English (Queen Anne) wine gallon was standardized as 231 in3 (133 imp fl oz; 3,790 mL) in the 1706 Act 5 Anne c27, but it differed before that:
• London 'Guildhall' gallon (before 1688) was 129.19 imp fl oz (3,671 mL)
• Jersey gallon (from 1562 onwards) was 139.20 imp fl oz (3,955 mL)
• Guernsey gallon (17th century origins till 1917) was 150.14 imp fl oz (4,266 mL)
• Irish gallon was 217 in3 (125 imp fl oz; 3,560 mL) (1495 Irish Act 10 Hen VII c22 confirmed by 1736 Act Geo II c9)

### Imperial gallon

A Shell petrol station selling 2* and 4* (leaded petrol) by the gallon in the UK, circa 1980

The British imperial gallon is defined as exactly 4.54609 dm3.[4] It is used in some Commonwealth countries, and until 1976 was defined as the volume of 10 pounds (4.5359237 kg) of water at 62 degrees Fahrenheit (16.67 °C).[5][6] There are four quarts in a gallon, the imperial pint is defined as 0.56826125 litres (18 gallon) and there are 20 imperial fluid ounces in an imperial pint,[4] yielding 160 fluid ounces in an imperial gallon.

### US liquid gallon

A fuel station in the United States displaying fuel prices per US gallon

The US liquid gallon (frequently called simply "gallon") is legally defined as 231 cubic inches, which is exactly 3.785411784 litres.[7][8] A US liquid gallon can contain about 3.785 kilograms or 8.34 pounds of water at 3.98 °C (39.16 °F), and is about 16.7% less than the imperial gallon. There are four quarts in a gallon, two pints in a quart and 16 US fluid ounces in a US pint, which makes the US fluid ounce equal to 1/128 of a US gallon. In order to overcome the effects of expansion and contraction with temperature when using a gallon to specify a quantity of material for purposes of trade, it is common to define the temperature at which the material will occupy the specified volume. For example, the volume of petroleum products[9] and alcoholic beverages[10] are both referenced to 60 °F (15.6 °C) in government regulations.

### US dry gallon

Since the dry measure is one-eighth of a US Winchester bushel of 2150.42 cubic inches, it is equal to exactly 268.8025 cubic inches, which is 4.40488377086 L.[11] The US dry gallon is not used in commerce, and is also not listed in the relevant statute, which jumps from the dry pint to the bushel.[12]

## Worldwide usage

Petrol units used in the world:
US gallon
Imperial gallon
No data

### Imperial gallon

As of 2021, the imperial gallon continues to be used as the standard petrol unit in four British Overseas Territories (Anguilla,[13] the British Virgin Islands,[14] the Cayman Islands,[15] and Montserrat)[16][17] and six countries (Antigua and Barbuda,[18] Dominica,[19] Grenada,[20][21] Saint Christopher and Nevis,[22] Saint Lucia,[23] and Saint Vincent and the Grenadines).[24]

All ten of the countries and territories which use the imperial gallon as their petrol unit also use miles per hour for speed limits, and drive on the left side of the road.

The United Arab Emirates ceased selling petrol by the imperial gallon in 2010 and switched to the litre, with Guyana following suit in 2013.[25][26][27]

Burma subsequently switched from the imperial gallon to the litre in 2014.[28]

Antigua and Barbuda has proposed switching to selling petrol by litres since 2015.[29][18]

The gallon was removed from the list of legally defined primary units of measure catalogued in the EU directive 80/181/EEC for trading and official purposes, with effect from 31 December 1994. Under the directive the gallon could still be used, but only as a supplementary or secondary unit.[30] One of the effects 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.[31][32][33] However within the United Kingdom and Ireland, barrels and large containers of beer, oil and other fluids are sometimes marked in imperial gallons, as 50 litres is very close to 11 imperial gallons.

Ireland also passed legislation in response to the EU directive, with the effective date being 31 December 1993.[34] Though the gallon has ceased to be a primary unit of trade, it can still be legally used in both the UK and Ireland as a supplementary unit.

Miles per imperial gallon is used as the primary fuel economy unit in the United Kingdom and as a supplementary unit in Canada on official documentation.[35][36][37]

In the Middle East, water-chiller bottles come in multiples of the imperial gallon.

### US liquid gallon

Other than the United States, petrol is sold by the US gallon in Belize, Colombia, Dominican Republic, Ecuador, Guatemala, Haiti, Honduras, Nicaragua, and Peru, as well as in the Marshall Islands, Federated States of Micronesia, and Palau, which are associated with the United States. Liberia, a former protectorate of the United States, uses US gallon when selling petrol.[38]

Despite its status as a US territory, and unlike American Samoa,[39] the Northern Mariana Islands,[40] Guam,[41] and the US Virgin Islands,[42] Puerto Rico ceased selling petrol by the US gallon in 1980.[43]

Panama ceased selling petrol in US gallons in 2013 and uses litres, while El Salvador followed suit in June 2021.[44]

In the Turks and Caicos Islands, both the US gallon and imperial gallon are used due to an increase in tax duties which was disguised by levying the same duty on the US gallon (3.79 L) as was previously levied on the Imperial gallon (4.55 L).[45]

The Bahamas also uses both the US gallon and imperial gallon.[46][47]

## Relationship to other units

Both the US liquid and imperial gallon are divided into four quarts (quarter gallons), which in turn are divided into two pints, which in turn are divided into two cups, (not in customary use outside the US), which in turn are further divided into two gills. Thus, both gallons are equal to four quarts, eight pints, sixteen cups, or thirty-two gills.

The imperial gill is further divided into five fluid ounces, whereas the US gill is divided into four fluid ounces, meaning an imperial fluid ounce is 1/20 of an imperial pint, or 1/160 of an imperial gallon, while a US fluid ounce is 1/16 of a US pint, or 1/128 of a US gallon. Thus, the imperial gallon, quart, pint, cup and gill are approximately 20% larger than their US counterparts, meaning these are not interchangeable, but the imperial fluid ounce is only approximately 4% smaller than the US fluid ounce, meaning these are often used interchangeably.

Historically, a common bottle size for liquor in the US was the "fifth", i.e. one-fifth of a US gallon (or one-sixth of an imperial gallon). While spirit sales in the US were switched to metric measures in 1976, a 750 mL bottle is still sometimes known as a "fifth".[48][49]

## History

An American milk bottle with a volume of one US gallon

The term derives most immediately from galun, galon in Old Norman French,[50] but the usage was common in several languages, for example jale in Old French and gęllet (bowl) in Old English. This suggests a common origin in Romance Latin, but the ultimate source of the word is unknown.[51]

The gallon originated as the base of systems for measuring wine and beer 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 one either the ale gallon or the larger imperial gallon.

By the end of the 18th century, there were three definitions of the gallon in common use:

• The corn gallon, or Winchester gallon, of about 268.8 cubic inches (≈ 4.405 L),
• The wine gallon, or Queen Anne's gallon, which was 231 cubic inches[52] (≈ 3.785 L), and
• The ale gallon of 282 cubic inches (≈ 4.622 L).

The corn or dry gallon is used (along with the dry quart and pint) in the United States for grain and other dry commodities. It is one-eighth of the (Winchester) bushel, originally defined as a cylindrical measure of 18+1/2 inches in diameter and 8 inches in depth, which made the dry gallon 8 in × (9+1/4 in)2 × π ≈ 2150.42017 cubic inches. The bushel was later defined to be 2150.42 cubic inches exactly, thus making its gallon exactly 268.8025 in3 (4.40488377086 L); in previous centuries, there had been a corn gallon of between 271 and 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 6 inches deep and 7 inches in diameter, i.e. 6 in × (3+1/2 in)2 × π ≈ 230.907 06 cubic inches. It was redefined during the reign of Queen Anne in 1706 as 231 cubic inches exactly, the earlier definition with π approximated to 22/7.

${\displaystyle \pi r^{2}h\approx {\frac {22}{7}}\times \left({\frac {7}{2}}\right)^{2}\times 6={\frac {(11\times 2)}{7}}\times {\frac {(7\times 7)}{(2\times 2)}}\times (2\times 3)=11\times 7\times 3=231}$

Although the wine gallon had been used for centuries for import duty purposes, there was no legal standard of it in the Exchequer, while a smaller gallon (224 cu in) was actually in use, requiring this statute; 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-litre relationship, the imperial gallon was based on the volume of 10 pounds of distilled water weighed in air with brass weights with the barometer standing at 30 inches of mercury and at a temperature of 62 °F.

In 1963, this definition was refined as the space occupied by 10 pounds of distilled water of density 0.998859 g/mL weighed in air of density 0.001217 g/mL against weights of density 8.136 g/mL (the original "brass" was refined as the densities of brass alloys vary depending on metallurgical composition), which was calculated as 4.546091879 L to ten significant figures.[5]

The precise definition of exactly 4.54609 cubic decimetres (also 4.54609 L, ≈ 277.419433 in3) came after the litre was redefined in 1964. This was adopted shortly afterwards in Canada, and adopted in 1976 in the United Kingdom.[5]

### Sizes of gallons

Historically, gallons of various sizes were used in many parts of Western Europe. In these localities, it has been replaced as the unit of capacity by the litre.

Comparison of gallons
Volume Definition Inverted
volume
(gal/cu ft)
Weight as
water at 62 °F
(pounds/gal)
Cylindrical approximation
(cu in) (dm3) Diameter
(in)
Height
(in)
Volume rel.
error
(%)
Current gallons
231 3.785411784 Statute of 5 Queen Anne (UK wine gallon, standard US gallon) 7.48 8.33 7 6 0.04
268.8025 4.40488377086 Winchester, statute of 13 & 14 William III (corn gallon, US dry gallon) 6.43 9.71 18.5 1 0.00001
≈ 277.4194 4.54609 Standard imperial gallon ≈ 6.23 10 5⅔ 11 0.0002
Historic gallons
216 (Roman unciae) ≈ 3.53961 Roman congius 8 7.8 5 11 0.01
224 ≈ 3.67070 Preserved at the Guildhall, London (old UK wine gallon) 7.71 8.09 9 3.5 0.6
264.8 ≈ 4.33929 Ancient Rumford quart (1228) 6.53 9.57 7.5 6 0.1
265.5 ≈ 4.35077 Exchequer (Henry VII, 1497, with rim) 6.51 9.59 13 2 0.01
266.25 ≈ 4.36306 Ancient Rumford (1228)
271 ≈ 4.44089 Exchequer (1601, E.) (old corn gallon) 6.38 9.79 4.5 17 0.23
272 ≈ 4.45728 Corn gallon (1688)
≈ 277.2026 ≈ 4.54254 Statute of 12 Anne (coal gallon) = 33/32 corn gallons 6.23 10
≈ 277.274 ≈ 4.54370 Imperial gallon, as originally determined in 1824 6.23 10
≈ 277.4195 4.546091879 Imperial gallon as re-determined in 1895 and defined in 1963 ≈ 6.23 10
278 ≈ 4.55560 Exchequer (Henry VII, with copper rim) 6.21 10.04
278.4 ≈ 4.56216 Exchequer (1601 and 1602 pints) 6.21 10.06
280 ≈ 4.58838 Exchequer (1601 quart) 6.17 10.1
282 ≈ 4.62115 Treasury (beer and ale gallon pre-1824) 6.13 10.2

## References

1. ^ Thompson, E Ambler; Taylor, Barry N (2008). "Guide for the use of the International System of Units (SI)". National Institute of Standards and Technology. doi:10.6028/nist.sp.811e2008. Retrieved 28 April 2022. {{cite journal}}: Cite journal requires |journal= (help); Missing |author2= (help)
2. ^ IEEE Std 260.1-2014
3. ^ Ricketts, Carl. "Capacity Measures of the British Isles" (PDF). Archived from the original (PDF) on 7 October 2016. Retrieved 6 September 2016.
4. ^ a b "Weights and Measures Act 1985, chapter 72, schedule 1". legislation.gov.uk. The National Archives on behalf of HM Government. Retrieved 7 June 2019.
5. ^ a b c BS 350:Part 1:1974 Conversion factors and tables Part 1. Basis of tables. Conversion factors (AMD 4153 ed.). British Standards Institution. 1983. p. Foreword. Before that date (November 1976) the definition in the Weights and Measures Act 1963 was such that the gallon could be calculated to be 4.546 091 879 dm3 to ten significant figures... The return, in November 1976, by precise definition to what had earlier been used as an approximation for the value of the gallon (i.e. 4.546 09 dm3)...
6. ^ BS 350:Part 1:1974 Conversion factors and tables Part 1. Basis of tables. Conversion factors (prior to Amendment No.1 1983 ed.). British Standards Institution. 1974. p. 10. the UK gallon (imp gal), defined in Schedule 1 of the Weights and Measures Act 1963, as the space occupied by 10 pounds of distilled water under certain conditions specified in the schedule.
7. ^ "NIST Handbook 44 - 2012 Edition Appendix C "General Tables of Units of Measurement"". Nist: C-5. 26 October 2012.
8. ^ Uniform Laws and Regulations in the areas of legal metrology and engine fuel quality (PDF). US Department of Commerce, National Institute of Standards and Technology. 2011. pp. 9–13, 69.
9. ^ "State of New Hampshire Dept of Weights and Measure" (PDF). Archived from the original (PDF) on 13 April 2012.
10. ^ "27 CFR section 5.21" (PDF). Gpo.gov. Retrieved 29 January 2022.
11. ^ "US Dry Conversion Calculator". High accuracy calculation for life or science. Retrieved 24 October 2019.
12. ^ Authorized tables, US Code, Title 15, ch. 6, subchapter I, sec. 205, accessed 19 July 2008.
13. ^ "Anguilla Renewable Energy Integration Project Final Report" (PDF). Anguilla RE Integration Final Report. Government of Anguilla Ministry of Infrastructure, Communications, Utilities, and Housing (MICUH). 19 October 2012. p. 104. Retrieved 13 October 2013. In 2008—the most recent year where WTI crude oil averaged US$100 per barrel—ANGLEC paid an average of about US$4 per imperial gallon (imp gal) for diesel.
14. ^ Walker, William (5 September 2012). "Biwater project draws scrutiny". Archived from the original on 2 October 2013. Retrieved 30 September 2013.
15. ^ Wilson, Stuart (9 May 2013). "Fuel costs driven by factors". Cayman Compass. Archived from the original on 22 December 2015. Retrieved 30 September 2013.
16. ^ "Petrol price increases, diesel decreases, cost of living goes up". The Montserrat Reporter. 30 November 2012.
17. ^ Htin Lynn Aung (22 September 2017). "Fuel prices on the rise". The Myanmar Times.
18. ^ a b "Government of Antigua and Barbuda". ab.gov.ag. Retrieved 5 May 2021.
19. ^ "Photo of the day: Up and up it goes". Dominica News Online. 10 May 2011.
20. ^
21. ^ "Authorities in Dominica reduce fuel prices". Antigua Observer Newspaper. 20 May 2020. Retrieved 5 May 2021.
22. ^ Thomas, Steve (5 September 2008). "Gas prices capped under $18 – lowest since July". The St. Kitts-Nevis Observer. Archived from the original on 24 May 2012. 23. ^ "Rotary has a new President - St. Lucia Voice News". Archived from the original on 22 December 2015. 24. ^ "Another service station sues SOL over fuel volume discrepancy". iWitness News. 26 April 2012. 25. ^ "Petrol stations in UAE go the metric route". gulfnews.com. Retrieved 5 May 2021. 26. ^ "End of road for imperial gallon as UAE switches to buying fuel by litre". The National. 15 December 2009. Retrieved 5 May 2021. 27. ^ "Gas prices at Guyoil stations remain below$1,000 mark | Caribbean Mi…". Archive.is. 28 June 2013. Archived from the original on 28 June 2013. Retrieved 5 May 2021.
28. ^ "Petrol Prices March 2014 in Yangon, Myanmar". Oilseedcrops.org. 5 April 2014.
29. ^ "The Re-Launch of Antigua And Barbuda's Metrication Programme". Diversity Global Magazine. 2013. Archived from the original on 16 January 2012. Retrieved 20 May 2013.
30. ^ The Council of the European Communities (9 February 2000). "Council Directive 80/181/EEC of 20 December 1979 on the approximation of the laws of the Member States relating to Unit of measurement and on the repeal of Directive 71/354/EEC". Retrieved 7 February 2009. The legal units of measurement ... for economic, public health, public safety or administrative purposes ... litre
31. ^ "The Units of Measurement Regulations 1995 (Article 4)". 13 July 1995. Retrieved 1 December 2011.
32. ^ "Units of Measurement Directive". LACORS. 1995. Archived from the original on 24 April 2012. Retrieved 26 November 2011.
33. ^ "Guidance Note on the use of Metric Units of Measurement by the Public Sector" (PDF). Department of Trade and Industry. 1995. Archived from the original (PDF) on 7 February 2011. Retrieved 20 March 2017.
34. ^ "S.I. No. 255/1992 — European Communities (Units of Measurement) Regulations, 1992". Irish Statute Book. Office of the Attorney General. 9 September 1992. Retrieved 1 December 2011.
35. ^ "FAQs – Fuel Consumption Program". Transport Canada. 5 November 2008. Archived from the original on 20 May 2010. Retrieved 31 July 2018.
36. ^ Statutory Instrument 2001/3523 Environmental Protection - The Passenger Car (Fuel Consumption and CO2 Emissions Information) Regulations 2001 (PDF). The Stationery Office. 30 October 2001. ISBN 0-11-038743-0. Retrieved 1 December 2011.
37. ^ Canada, Natural Resources (30 April 2018). "energuide-vehicles". Nrcan.gc.ca. Retrieved 21 February 2021.
38. ^
39. ^ "Gasoline goes up eleven cents per gallon tomorrow". Samoa News. Archived from the original on 4 March 2016.
40. ^ Dones, Liberty (17 May 2006). "Shell pump prices up 8 cents". Saipan Tribune. Archived from the original on 30 October 2006. Retrieved 30 September 2013.
41. ^ "UPDATE: Gas prices down 10 cents to \$4.73 for a gallon of unleaded". Pacific Daily News. Archived from the original on 30 September 2013.
42. ^ Blackburn, Joy (16 July 2012). "7-cent-per-gallon WAPA tax goes into effect". Virgin Islands Daily News. Archived from the original on 30 September 2013.
43. ^ Pesquera de Busquets, Carmen T; Barcelo, Carlos Romero (14 June 1979), Order to establish the price of half 1/2 galon [sic] of gasoline as transitory measure and that the litter [sic] should be the final metric measurement for the sale of gasoline in Puerto Rico (PDF), San Juan, Puerto Rico: Departamento de Asuntos del Consumidor, retrieved 21 May 2013
44. ^ "La gasolina se venderá en litros y otros productos se pesarán en kilogramos, según nuevo sistema métrico a implementarse en 2021 | Noticias de El Salvador". Noticias de El Salvador - elsalvador.com (in Spanish). 16 December 2020. Retrieved 5 May 2021.
45. ^ "New Measures to Improve TCI Finances And Prioritise Spending". TheBahamasWeekly.com.
46. ^ "OFFICIAL GAZETTE THE BAHAMAS PUBLISHED BY AUTHORITY : NASSAU" (PDF). Laws.bahamas.gov.bs. 12 February 2014. Retrieved 29 January 2022.
47. ^ "Archived copy". Archived from the original on 2 June 2021. Retrieved 1 June 2021.{{cite web}}: CS1 maint: archived copy as title (link)
48. ^ E. Frank Henriques, The Signet Encyclopedia of Wine, p. 298
49. ^ Cherry, Rona (11 October 1976). "Liquor Industry Converts to Metric System". The New York Times.
50. ^ Chisholm, Hugh, ed. (1911). "Gallon" . Encyclopædia Britannica. Vol. 11 (11th ed.). Cambridge University Press. p. 421.
51. ^ "gallon, n.". Oxford English Dictionary (2 ed.). Oxford, England: Oxford University Press. 1989.
52. ^ "English wine gallon". Sizes.com. Retrieved 17 June 2010.