Imperial units

The former Weights and Measures office in Seven Sisters, London (590 Seven Sisters Road)

The imperial system of units, imperial system or imperial units (also known as British Imperial or Exchequer Standards of 1826) is the system of units first defined in the British Weights and Measures Act 1824 and which continued to be developed through a series of Weights and Measures Acts and amendments.

The imperial system developed from earlier English units as did the related but differing system of customary units of the United States. The imperial units replaced the Winchester Standards, which were in effect from 1588 to 1825. The system came into official use across the British Empire in 1826.

By the late 20th century, most nations of the former empire had officially adopted the metric system as their main system of measurement, but imperial units are still used alongside metric units in the United Kingdom and in some other parts of the former empire, notably Canada.

The modern UK legislation defining the imperial system of units is given in the Weights and Measures Act 1985 (as amended).

Implementation

The Weights and Measures Act 1824 was initially scheduled to go into effect on 1 May 1825. The Weights and Measures Act 1825 pushed back the date to 1 January 1826. The 1824 act allowed the continued use of pre-imperial units provided that they were customary, widely known, and clearly marked with imperial equivalents.

Apothecaries' units

Imperial standards of length 1876 in Trafalgar Square, London

Apothecaries' units are not mentioned in the acts of 1824 and 1825. At the time, apothecaries' weights and measures were regulated "in England, Wales, and Berwick-upon-Tweed" by the London College of Physicians, and in Ireland by the Dublin College of Physicians. In Scotland, apothecaries' units were unofficially regulated by the Edinburgh College of Physicians. The three colleges published, at infrequent intervals, pharmacopoeias, the London and Dublin editions having the force of law.

Imperial apothecaries' measures, based on the imperial pint of 20 fluid ounces, were introduced by the publication of the London Pharmacopoeia of 1836, the Edinburgh Pharmacopoeia of 1839, and the Dublin Pharmacopoeia of 1850. The Medical Act 1858 transferred to the Crown the right to publish the official pharmacopoeia and to regulate apothecaries' weights and measures.

Units

Length

Metric equivalents in this article usually assume the latest official definition. Previously, the most precise measurement of the imperial Standard Yard was 0.914398415 metres.

Table of length equivalent units
Unit Abbr. or symbols Relative to previous Feet Metres Notes
twip 1⁄17280 0.000017638 typographic measure
thou th 1.44 twip 1⁄12000 0.0000254

Abbreviation of "thousandth of an inch". Also known as mil.

barleycorn Bc 333+1⁄3 th 1⁄36 0.00846 1⁄3 in
inch in (″) 3 Bc 1⁄12 0.0254 1 metre ≡ 39 47⁄127 inches
hand hh 4 in 1⁄3 0.1016 Used to measure the height of horses
foot ft (′) 3 hh 1 0.3048 12 in
yard yd 3 ft 3 0.9144 Defined as exactly 0.9144 m by the international yard and pound agreement of 1959
rod rd 5+1⁄2 yd 16+1⁄2 5.0292 The rod is also called pole or perch
furlong fur 40 rd 660 201.168 220 yd
mile mi 8 furlongs 5280 1609.344 1760 yd or 80 chains
league lea 3 miles 15840 4828.032
Maritime units
fathom ftm 2.02667 yd 6.0761 1.852 The British Admiralty in practice used a fathom of 6 ft. This was despite its being 1⁄1000 of a nautical mile (i.e. 6.08 ft) until the adoption of the international nautical mile.
cable 100 fathoms 607.61 185.2 One tenth of a nautical mile. Equal to 100 fathoms under the strict definition.
nautical mile nmi 10 cables 6076.1 1852 Used for measuring distances at sea (and also in aviation) and approximately equal to one arc minute of a great circle. Until the adoption of the international definition of 1852 m in 1970, the British nautical (Admiralty) mile was defined as 6080 ft.
Gunter's survey units (17th century onwards)
link 1⁄1000 fur 66⁄100 0.201168 Decimalization of furlong and acre to facilitate surveying calculations
chain ch 100 links 66 20.1168 4 rods or 1⁄10 of a furlong. The distance between the two wickets on a cricket pitch.

Area

Table of area units and equivalents
Unit Abbr. or symbol Relative to previous Relation to units of length Square feet Square yards Acres Square metres Hectares
perch* 1 rd × 1 rd 272+1⁄4 30+1⁄4 1⁄160 25.29285264 0.002529285264
rood 40 perches 1 furlong × 1 rd 10890 1210 1⁄4 1011.7141056 0.10117141056
acre 4 roods 1 furlong × 1 chain 43560 4840 1 4046.8564224 0.40468564224
square mile sq mi 640 acres 1 mile × 1 mile 27878400 3097600 640 2589988.110336 258.9988110336
Note: *The square rod has been called a pole or perch or, more properly, square pole or square perch for centuries.

Volume

Imperial volume units, illustrated as jugs of various sizes

The Weights and Measures Act 1824 invalidated the various different gallons in use in the British Empire, declaring them to be replaced by the statute gallon (which became known as the imperial gallon), a unit close in volume to the ale gallon. The 1824 act defined the volume of a gallon to be that of 10 pounds (4.54 kg) of distilled water weighed in air with brass weights with the barometer standing at 30 inches of mercury (102 kPa) at a temperature of 62 °F (17 °C). The 1824 act went on to give this volume as 277.274 cubic inches (4.54371 litres). The Weights and Measures Act 1963 refined this definition to be the volume of 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, which works out to 4.546092 L. The Weights and Measures Act 1985 defined a gallon to be exactly 4.54609 L (approximately 277.4194 cu in).

Table of equivalences
Unit Imperial
ounces		 Imperial
pints		 Millilitres Cubic inches US ounces US pints
fluid ounce (fl oz) 1     1⁄20     28.41306251.73390.960760.060047
gill (gi) 5     1⁄4     142.06531258.66944.80380.30024
pint (pt) 20     1     568.2612534.67719.2151.2009
quart (qt) 40     2     1136.522569.35538.4302.4019
gallon (gal) 160     8     4546.09277.42153.729.6076
Note: The millilitre equivalences are exact, but cubic-inch and US measures are correct to 5 significant figures.
Unit measures defined by the Weights and Measures Act 1824,
all measures determined by reference to the statute gallon of 277.274 cubic inches.
Unit gallons Capacity
pint 1⁄834.76 cu in (569.6 mL; 0.5696 L)
quart 1⁄469.32 cu in (1.1360 L)
gallon 1277.274 cu in (4.54371 L)
peck 2554.548 cu in (9.08741 L)
bushel 82,218.192 cu in (36.34965 L)
quarter 6417,745.536 cu in (290.79723 L)
Note: The 1824 Act removed the distinction between liquid and dry measure, specifying instead that
the dry quantities shall be unheaped. The metric equivalences shown are approximate.

British apothecaries' volume measures

These measurements were in use from 1826, when the new imperial gallon was defined. For pharmaceutical purposes, they were replaced by the metric system in the United Kingdom on 1 January 1971. In the US, though no longer recommended, the apothecaries' system is still used occasionally in medicine, especially in prescriptions for older medications.

Table of British apothecaries' volume units
Unit Symbols and
abbreviations		 Relative to
previous		 Exact
metric value
minim ♏︎, , m, m., min   (1⁄9600 pint) 59.1938802083 μL
fluid scruple fl ℈, fl s 20 minims (1⁄480 pint) 1.18387760416 mL
fluid drachm
(fluid dram, fluidram)		 ʒ, fl ʒ, fʒ, ƒ 3, fl dr 3 fluid scruples (1⁄160 pint) 3.5516328125 mL
fluid ounce ℥, fl ℥, f℥, ƒ ℥, fl oz 8 fluid drachms 28.4130625 mL
pint O, pt 20 fluid ounces 568.26125 mL
gallon C, gal 8 pints 4.54609 L
Note:
  1. ↑ The vinculum over numbers (e.g. 3) represents a repeating decimal.

Mass and weight

In the 19th and 20th centuries, the UK used three different systems for mass and weight.

The distinction between mass and weight is not always clearly drawn. Strictly a pound is a unit of mass, but it is commonly referred to as a weight. When a distinction is necessary, the term pound-force may refer to a unit of force rather than mass. The troy pound (373.2417216 g) was made the primary unit of mass by the Weights and Measures Act 1824 and its use was abolished in the UK on 1 January 1879, with only the troy ounce (31.1034768 g) and its decimal subdivisions retained. The Weights and Measures Act 1855 made the avoirdupois pound the primary unit of mass. In all the systems, the fundamental unit is the pound, and all other units are defined as fractions or multiples of it.

Table of mass units
Unit Pounds In SI units Notes
grain (gr) 1⁄7000 64.79891 mg Exactly 64.79891 milligrams.
drachm (dr) 1⁄256 1.7718451953125 g A dram is 1⁄16 of an ounce
ounce (oz) 1⁄16 28.349523125 g An ounce is 1⁄16 of a pound
pound (lb) 1 0.45359237 kg Defined by the Units of Measurement Regulations 1994 (SI 1994/2867)
stone (st) 14 6.35029318 kg The plural stone is often used when providing a weight (e.g. "this sack weighs 8 stone"). A person's weight is usually quoted in stone and pounds in English-speaking countries that use the avoirdupois system, with the exception of the United States and Canada, where it is usually quoted in pounds.
quarter (qr or qtr) 28 12.70058636 kg One quarter (literally a quarter of a hundredweight) is equal to two stone or 28 pounds. The term quarter is also used in retail contexts, where it refers to four ounces, i.e. a quarter of a pound. (The 1824 act defined a quarter as a unit of volume, as above: thus a 'quarter of wheat', 64 gallons, would weigh about 494 lb.).
hundredweight (cwt) 112 50.80234544 kg One imperial hundredweight is equal to eight stone. This is the long hundredweight, 112 pounds, as opposed to the short hundredweight of 100 pounds used in the United States and Canada.
ton (ton) 2240 1016.0469088 kg Twenty hundredweight equals a ton (as in the US and Canadian systems). The imperial hundredweight is 12% greater than the US and Canadian one. The imperial ton (or long ton) is 2240 pounds, which is much closer to a tonne (about 2204.6 pounds), compared to the 10.7% smaller North American short ton of 2000 pounds (907.185 kg). The symbol "t" is used to denote a tonne.
Gravitational units
slug (slug) 32.17404856 14.59390294 kg The slug, a unit associated with imperial and US customary systems, is a mass that accelerates by 1 ft/s2 when a force of one pound (lbf) is exerted on it.
F = ma (Newton's second law)
1 lbf = 1 slug × 1 ft/s2 (as defined above)
1 lbf = 1 lb × g/gc (by definition of the pound force[citation needed])
g ≈ 32.17404856 ft/s2
gc ≈ 32.17404856 lbm⋅ft/lbf⋅s2
1 slug ≈ 32.17404856 pounds

Natural equivalents

The 1824 Act of Parliament defined the yard, pound and gallon by reference to the prototype standards, naming the prototypes the Imperial Standard Yard, the Imperial Standard Troy Pound and the Imperial Standard Gallon, and it also defined the values of certain physical constants, to make provision for re-creation of the standards if they were to be damaged. For the yard, the length of a pendulum beating seconds at the latitude of Greenwich at mean sea level in vacuo was defined as 39.1393 inches. For the pound, the mass of a cubic inch of distilled water at an atmospheric pressure of 30 inches of mercury and a temperature of 62° Fahrenheit was defined as 252.458 grains, with there being 7,000 grains per pound.

Following the destruction of the original prototypes in the 1834 Houses of Parliament fire, it proved impossible to recreate the standards from these definitions, and a new Weights and Measures Act 1855 was passed which permitted the recreation of the prototypes from recognized secondary standards.

Current use

Countries using the metric (SI), imperial and US customary systems as of 2019

United Kingdom

A baby bottle marked in metric, imperial (UK) and US customary units

As of 2026, imperial units remain in everyday use in the United Kingdom. They are used for road distances and speeds, draught beer and cider, personal height and body weight, some sports and property advertising, and many pre-packaged foods are still produced in imperial sizes.

Imperial units are defined in law in terms of their metric equivalents by the Weights and Measures Act 1985. They remain authorised as primary units for road traffic signs and for distance and speed measurement (the mile, yard, foot and inch), for draught beer and cider and milk in returnable containers (the pint), and for transactions in precious metals (the troy ounce). Draught beer and cider must be sold in pints, half-pints or third-pints. Since September 2024, still and sparkling wine may also be sold in pint (568 ml) bottles. In other trade, imperial units may be shown only as supplementary indications alongside metric units and no more prominently. In 2023 the government decided to keep this rule following a public consultation.

Road signs give distances in miles and yards and speed limits in miles per hour. Height and width restriction signs are given in feet and inches, with metric equivalents required on new signs since March 2015. Vehicle speedometers must be able to display miles per hour, and fuel economy is commonly quoted in miles per gallon.[citation needed] Tyre pressures are commonly given in pounds per square inch, usually alongside bar. On the national rail network, locations such as bridges and junctions are identified by their distance in miles and chains from a fixed origin.

Many people use miles, yards, feet and inches for distance and height, and pints for milk and beer. Body weight is widely given in stones and pounds for adults and in pounds and ounces for babies, and NHS material aimed at the public gives weight and height in imperial units as well as metric. A 2015 YouGov survey found that many people did not know their weight or height in both systems, and that people under 40 preferred metric units while those aged 40 and over preferred imperial.

In horse racing, race distances are given in miles, furlongs and yards, and the weights carried by horses in stones and pounds. The height of horses is measured in hands of 4 inches (102 mm).[citation needed] A cricket pitch is 22 yards (20 m) long under the Laws of Cricket, and golf course and hole lengths are given in yards.[citation needed]

Land and property are commonly advertised in acres and square feet.[citation needed] Office rents are quoted per square foot per year. Older gas meters record consumption in cubic feet.

Television and monitor display sizes are given in inches, measured diagonally. Clothing such as trousers and shirt collars is commonly sized in inches.[citation needed] Food sold by length or diameter, such as pizzas and sandwiches, is usually described in inches.[citation needed] Steel pipe is sized in inches,[citation needed] and off-road bicycle frames are measured in inches.[citation needed]

Many pre-packaged foods are produced in imperial quantities but labelled only in metric. A 1 lb (454 g) tin of Lyle's Golden Syrup, for example, is labelled 454 g with no imperial equivalent shown. Jam and marmalade are commonly sold in 340 g (12 oz) and 454 g (1 lb) jars, and many packs of sausages weigh 454 g.[citation needed]

India

India began converting to the metric system from the imperial system between 1955 and 1962. The metric system in weights and measures was adopted by the Indian Parliament in December 1956 with the Standards of Weights and Measures Act, which took effect beginning 1 October 1958. By 1962, metric units became "mandatory and exclusive."

Today all official measurements are made in the metric system. In common usage some older Indians may still refer to imperial units. Some measurements, such as the heights of mountains, are still recorded in feet. Tyre rim diameters are still measured in inches, as used worldwide. Industries like the construction and the real estate industry still use both the metric and the imperial system though it is more common for sizes of homes to be given in square feet and land in acres.

In Standard Indian English, as in Australian, Canadian, New Zealand, Singaporean, and British English, metric units such as the litre, metre, and tonne utilise the traditional spellings brought over from French, which differ from those used in the United States and the Philippines. The imperial long ton is invariably spelt with one 'n'.

Hong Kong

Hong Kong has three main systems of units of measurement in current use:

In 1976 the Hong Kong Government started the conversion to the metric system, and as of 2012 measurements for government purposes, such as road signs, are almost always in metric units. All three systems are officially permitted for trade, and in the wider society a mixture of all three systems prevails.

The Chinese system's most commonly used units for length are 里 (lei5), 丈 (zoeng6), 尺 (cek3), 寸 (cyun3), 分 (fan1) in descending scale order. These units are now rarely used in daily life, the imperial and metric systems being preferred. The imperial equivalents are written with the same basic Chinese characters as the Chinese system. In order to distinguish between the units of the two systems, the units can be prefixed with "Ying" (英, jing1) for the imperial system and "Wa" (華, waa4) for the Chinese system. In writing, derived characters are often used, with an additional 口 (mouth) radical to the left of the original Chinese character, for writing imperial units. The most commonly used units are the mile or "li" (哩, li1), the yard or "ma" (碼, maa5), the foot or "chek" (呎, cek3), and the inch or "tsun" (吋, cyun3).

The traditional measure of flat area is the square foot (方呎, 平方呎, fong1 cek3, ping4 fong1 cek3) of the imperial system, which is still in common use for real estate purposes. The measurement of agricultural plots and fields is traditionally conducted in 畝 (mau5) of the Chinese system.

For the measurement of volume, Hong Kong officially uses the metric system, though the gallon (加侖, gaa1 leon4-2) is also occasionally used.

Canada

A one US gallon gas can purchased near the US-Canada border showing equivalences in imperial gallons and litres
Imperial and metric measurements on Canadian canned goods labels. The imperial measurements often take precedence over the metric ones on labels.

During the 1970s, the metric system and SI units were introduced in Canada to replace the imperial system. Within the government, efforts to implement the metric system were extensive; almost any agency, institution, or function provided by the government uses SI units exclusively. Imperial units were eliminated from all public road signs and both systems of measurement will still be found on privately owned signs, such as the height warnings at the entrance of a parkade. In the 1980s, momentum to fully convert to the metric system stalled when the government of Brian Mulroney was elected. There was heavy opposition to metrication and as a compromise the government maintains legal definitions for and allows use of imperial units as long as metric units are shown as well.

The law requires that measured products (such as fuel and meat) be priced in metric units and an imperial price can be shown if a metric price is present. There tends to be leniency in regards to fruits and vegetables being priced in imperial units only. Environment Canada still offers an imperial unit option beside metric units, even though weather is typically measured and reported in metric units in the Canadian media. Some radio stations near the United States border (such as CIMX and CIDR) primarily use imperial units to report the weather. Railways in Canada also continue to use imperial units.

Imperial units are still used in ordinary conversation. Today, Canadians typically use a mix of metric and imperial measurements in their daily lives. The use of the metric and imperial systems varies by age. The older generation mostly uses the imperial system, while the younger generation more often uses the metric system. Quebec has implemented metrication more fully. [citation needed] Newborns are measured in SI at hospitals, but the birth weight and length is also announced to family and friends in imperial units. Drivers' licences use SI units, though many English-speaking Canadians give their height and weight in imperial. In livestock auction markets, cattle are sold in dollars per hundredweight (short), whereas hogs are sold in dollars per hundred kilograms. Imperial units still dominate in recipes, construction, house renovation and gardening. Land is now surveyed and registered in metric units whilst initial surveys used imperial units. For example, partitioning of farmland on the prairies in the late 19th and early 20th centuries was done in imperial units; this accounts for imperial units of distance and area retaining wide use in the Prairie Provinces.

In English-speaking Canada commercial and residential spaces are mostly (but not exclusively) constructed using square feet, while in French-speaking Quebec commercial and residential spaces are constructed in metres and advertised using both square metres and square feet as equivalents. Carpet or flooring tile is purchased by the square foot, but less frequently also in square metres. Motor-vehicle fuel consumption is reported in both litres per 100 km and statute miles per imperial gallon, leading to the erroneous impression that Canadian vehicles are 20% more fuel-efficient than their apparently identical American counterparts for which fuel economy is reported in statute miles per US gallon (neither country specifies which gallon is used). Canadian railways maintain exclusive use of imperial measurements to describe train length (feet), train height (feet), capacity (tons), speed (mph), and trackage (miles).

Imperial units also retain common use in firearms and ammunition. Imperial measures are still used in the description of cartridge types, even when the cartridge is of relatively recent invention (e.g., .204 Ruger, .17 HMR, where the calibre is expressed in decimal fractions of an inch). Ammunition that is already classified in metric is still kept metric (e.g., 9×19mm). In the manufacture of ammunition, bullet and powder weights are expressed in terms of grains for both metric and imperial cartridges.

In keeping with the international standard, air navigation is based on nautical units, e.g., the nautical mile, which is neither imperial nor metric, and altitude is measured in imperial feet.

Australia

While metrication in Australia has largely ended the official use of imperial units, for particular measurements, international use of imperial units is still followed.

The influence of British and American culture in Australia has been noted to be a cause for residual use of imperial units of measure.

New Zealand

New Zealand introduced the metric system on 15 December 1976. Aviation was exempt, with altitude and airport elevation continuing to be measured in feet whilst navigation is done in nautical miles; all other aspects (fuel quantity, aircraft weight, runway length, etc.) use metric units.

Screen sizes for devices such as televisions, monitors and phones, and wheel rim sizes for vehicles, are stated in inches, as is the convention in the rest of the world - and a 1992 study found a continued use of imperial units for birth weight and human height alongside metric units.

Ireland

Ireland has officially changed over to the metric system since entering the European Union, with distances on new road signs being metric since 1997 and speed limits being metric since 2005. The imperial system remains in limited use – for sales of beer in pubs (traditionally sold by the pint). All other goods are required by law to be sold in metric units with traditional quantities being retained for goods like butter and sausages, which are sold in 454 grams (1 lb) packaging. The majority of cars sold pre-2005 feature speedometers with miles per hour as the primary unit, but with a kilometres per hour display. Often signs such as those for bridge height can display both metric and imperial units. Imperial measurements continue to be used colloquially by the general population especially with height and distance measurements such as feet, inches, and acres as well as for weight with pounds and stones still in common use among people of all ages. Measurements such as yards have fallen out of favour with younger generations. Ireland's railways still use imperial measurements for distances and speed signage. Property is usually listed in square feet as well as metres also.

Horse racing in Ireland still continues to use stones, pounds, miles and furlongs as measurements.

Bahamas

Imperial measurements remain in general use in the Bahamas.

Legally, both the imperial and metric systems are recognised by the Weights and Measures Act 2006.

Belize

Both imperial units and metric units are used in Belize. Both systems are legally recognized by the National Metrology Act.

Myanmar

According to the CIA, in June 2009, Myanmar was one of three countries that had not adopted the SI metric system as their official system of weights and measures. Metrication efforts began in 2011. The Burmese government set a goal to metricate by 2019, which was not met, with the help of the German National Metrology Institute.

Other countries

Some imperial measurements remain in limited use in Malaysia, the Philippines, Sri Lanka and South Africa. Measurements in feet and inches, especially for a person's height, are frequently encountered in conversation and non-governmental publications.

Prior to metrication, it was a common practice in Malaysia for people to refer to unnamed locations and small settlements along major roads by referring to how many miles the said locations were from the nearest major town. In some cases, these eventually became the official names of the locations; in other cases, such names have been largely or completely superseded by new names. An example of the former is Batu 32 (literally "Mile 32" in Malay), which refers to the area surrounding the intersection between Federal Route 22 (the Tamparuli-Sandakan highway) and Federal Route 13 (the Sandakan-Tawau highway). The area is so named because it is 32 miles west of Sandakan, the nearest major town.

Petrol is still sold by the imperial gallon in Anguilla, Antigua and Barbuda, Belize, Myanmar, the Cayman Islands, Dominica, Grenada, Montserrat, St Kitts and Nevis and St. Vincent and the Grenadines.[citation needed] The United Arab Emirates Cabinet in 2009 issued the Decree No. (270 / 3) specifying that, from 1 January 2010, the new unit sale price for petrol will be the litre and not the gallon, which was in line with the UAE Cabinet Decision No. 31 of 2006 on the national system of measurement, which mandates the use of International System of units as a basis for the legal units of measurement in the country. Sierra Leone switched to selling fuel by the litre in May 2011.

In October 2011, the Antigua and Barbuda government announced the re-launch of the Metrication Programme in accordance with the Metrology Act 2007, which established the International System of Units as the legal system of units. The Antigua and Barbuda government has committed to a full conversion from the imperial system by the first quarter of 2015.

In March 2025, Dubai completed the switch from imperial gallons to cubic metres as the unit to measure water consumption.

See also

Explanatory notes

  1. ↑ 10 pounds = 4535.9237 grams. @ 0.998859 g/mL => 4546.092 mL
  2. ↑ References for the Table of British apothecaries' volume units: Unit column;: C-7  Symbols & abbreviations column;: C-5, C-17–C-18  Relative to previous column;: C-7  Exact metric value column – fluid ounce, pint and gallon, all other values calculated using value for fluid ounce and the Relative to previous column's values.

Citations

  1. ↑ Britannica Educational Publishing (2010). The Britannica Guide to Numbers and Measurement. The Rosen Publishing Group. p. 241. ISBN 978-1-61530-218-5. Archived from the original on 14 January 2023. Retrieved 1 July 2015.
  2. ↑ Chaney, Henry James (1897). A Practical Treatise on the Standard Weights and Measures in Use in the British Empire with some account of the metric system. Eyre and Spottiswoode. p. 3. Retrieved 11 September 2016.
  3. ↑ "Weights and Measures Act 1985". legislation.gov.uk. Archived from the original on 2 January 2022. Retrieved 20 January 2020.
  4. 1 2 3 Great Britain (1824). The statutes of the United Kingdom of Great Britain and Ireland (1807-1865). His Majesty's statute and law printers. pp. 339–354. Retrieved 31 December 2011.
  5. ↑ Great Britain; William David Evans; Anthony Hammond; Thomas Colpitts Granger (1836). A collection of statutes connected with the general administration of the law: arranged according to the order of subjects. W. H. Bond. pp. 306–27. Retrieved 31 December 2011.
  6. ↑ Edinburgh medical and surgical journal. A. and C. Black. 1824. p. 398.
  7. ↑ Ireland; Butler, James Goddard; Ball, William (barrister.) (1765). The Statutes at Large, Passed in the Parliaments Held in Ireland: From the twenty-third year of George the Second, A.D. 1749, to the first year of George the Third, A.D. 1761 inclusive. Boulter Grierson. p. 852.
  8. ↑ Gray, Samuel Frederick (1836). A supplement to the Pharmacopœia and treatise on pharmacology in general: including not only the drugs and preparations used by practitioners of medicine, but also most of those employed in the chemical arts : together with a collection of the most useful medical formulæ ... Longman, Rees, Orme, Brown, Green, and Longman. p. 516. Retrieved 29 July 2012.
  9. ↑ "A Translation of the Pharmacopoeia of the Royal College of Physicians of London, 1836.: With ..." S. Highley, 32, Fleet Street. 1837.
  10. ↑ The Pharmacopoeia of the Royal College of Physicians of Edinburgh. Adam and Charles Black and Bell and Bradfute. 1839. pp. xiii–xiv.
  11. ↑ Royal College of Physicians of Dublin; Royal College of Physicians of Ireland (1850). The pharmacopœia of the King and queen's college of physicians in Ireland. Hodges and Smith. p. xxii. Retrieved 29 July 2012.
  12. ↑ Great Britain (1858). A collection of the public general statutes passed in the ... year of the reign of ... Printed by G. W. Eyre and W. Spottiswoode, Printers to the Queen. p. 306.
  13. ↑ Sears et al. 1928. Phil Trans A, 227:281.
  14. ↑ Jerrard and McNeill, Dictionary of Scientific Units, second edition, Chapman and Hall; cites first appearance in print in Journal of the Institution of Electrical Engineers (G.B.) vol. 1, page 246 (1872).
  15. ↑ The exact figure was 6.08 ft, but 6 ft was in use in practice. The commonly accepted definition of a fathom was always 6 feet. The conflict was inconsequential, as Admiralty nautical charts designated depths shallower than 5 fathoms in feet on older imperial charts. Today, all charts worldwide are metric, except for USA Hydrographic Office charts, which use feet for all depth ranges.
  16. ↑ The nautical mile was not readily expressible in terms of any of the intermediate units, because it was derived from the circumference of the Earth (like the original metre).
  17. ↑ "Appendix C: General Tables of Units of Measurements" (PDF). NIST. Archived from the original (PDF) on 26 November 2006. Retrieved 4 January 2007.
  18. 1 2 3 "An Act for ascertaining and establishing Uniformity of Weights and Measures (17 June 1824)" (PDF). legislation.gov.uk. 17 June 1824. p. 639,640. Archived (PDF) from the original on 20 July 2020. Retrieved 19 January 2020. Two such Gallons shall be a Peck, and Eight such Gallons shall be a Bushel, and Eight such Bushels a Quarter of Corn or other dry Goods, not measured by Heaped Measure.. (The date of coming into effect was 1 May 1825).
  19. ↑ imperial gallon. Sizes.com. 25 October 2013. Archived from the original on 14 May 2011. Retrieved 10 July 2019.
  20. ↑ "The Weights and Measures (Equivalents for dealings with drugs) Regulations 1970". Archived from the original on 20 June 2013. Retrieved 7 July 2012.
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