U. S. customary units, also known in the United States as English units or Imperial units (in reference to the British Empire)[1] (but see English unit for British standards) or standard units, are units of measurement that are currently used in the USA, in some cases alongside units from SI (International System of Units — the modern metric system). The United States of America —commonly referred to as the The British Empire was the largest empire in history and for over a century was the foremost global power. English unit is the American name for a unit in one of a number of systems of Units of measurement, some obsolete and some still in use in present-day USA, the The metric system is a decimalised system of measurement. It exists in several variations with different choices of base units, though the choice of base units does All units are defined in terms of SI base units, but at ratios inconvenient for conversion.

## History

The U. S. system of units is similar to the Imperial system which was used officially in the United Kingdom until 1995 [2] (and which still has official usage there for a few purposes, and unofficial usage for many others). Imperial units or the Imperial system is a collection of units first defined in the British Weights and Measures Act of 1824 The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located Both systems derive from the evolution of local units over the centuries, as a result of standardization efforts in England; the local units themselves mostly trace back to Roman and Anglo-Saxon units. England is a Country which is part of the United Kingdom. Its inhabitants account for more than 83% of the total UK population whilst its mainland Today, these units are defined in terms of SI units.

In the Omnibus Trade and Competitiveness Act of 1988, the United States government designated the metric system of measurement as "the preferred system of weights and measures for U. S. trade and commerce". The legislation states that the Federal Government has a responsibility to assist industry, especially small business, as it voluntarily converts to the metric system of measurement. This process of legislation and conversion is known as metrication, and in the U. Metrication (or metrification refers to the introduction of the SI metric system as the International standard for physical measurements—a long-term series S. is most evident in labeling requirements on food products, where SI units are almost always presented alongside customary units.

However, metrication in the United States has been less forcefully imposed than in other countries,[3] and has encountered more resistance from industrial and consumer market forces, so customary units are still widely used on consumer products and in industrial manufacturing; only in military, medical, and scientific contexts are SI units generally the norm. Metrication in the United States is the process of introducing the International System of units ( SI) to replace the Customary units of measurement Since everyday weights and measures are mostly non-SI, children in U. S. public schools are generally taught customary units before SI, although many schools are now attempting to teach SI units at an earlier age.

There are anecdotal objections to the use of metric units in carpentry and the building trades, on the basis that it is easier to remember an integer number of inches plus a fraction than a measurement in millimeters,[4] or that inch measurements are more suitable when distances are frequently divided by two. [3]

Other countries had (or still have, unofficially), customary units of their own, sometimes very similar in name and measure to the U. S. customary units, since they often shared the same Germanic or Roman origins. Frequently, however, these units designated quite different sizes. For example, in different countries, the mile ranged from one half to five US miles, and even foot and pound had varying definitions. A mile is a unit of Length, usually used to measure Distance, in a number of different systems including Imperial units United States A foot (plural feet or foot; symbol or abbreviation ft or sometimes &prime – the prime symbol) is a non-SI unit The pound or pound-mass (abbreviation lb, lbm, or sometimes in the United States #) is a unit of Mass Even within the USA, at least through the 19th century, the customary units of measure were sometimes just as variable. Eventually, most countries, including the United States, redefined their customary units in terms of SI units like kilogram and meter. The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International Often, though, unlike English units, they were rounded to "nice" SI values, leading to their use in colloquial speech, alongside SI terms, into the present day.

Historically, a wide range of non-SI units have been used in the United States, and on the British Isles before that, but many of these have fallen into disuse. This article only deals with the units commonly used or officially defined in the United States.

As of 2007, the U. S. customary units remain the last widely used official non-metric system of measurement as besides the United States only Liberia and Myanmar have not adopted the International System of Units as their primary or sole system of measurement. Liberia, officially the Republic of Liberia, is a country on the west coast of Africa, bordered by Sierra Leone, Guinea, Côte d'Ivoire Burma, officially the Union of Myanmar ( pjìdàunzṵ mjàmmà nàinŋàndɔ̀ is the largest country by geographical area in mainland Southeast Asia. [5]

## Units of length

The system for measuring length in the United States' customary system is based on the inch, foot, yard, and mile, which are the only four customary length measurements in everyday use. Inches redirects here To see the Les Savy Fav album see Inches. A foot (plural feet or foot; symbol or abbreviation ft or sometimes &prime – the prime symbol) is a non-SI unit A yard (abbreviation yd) is a unit of Length in several different systems including English units Imperial units and United A mile is a unit of Length, usually used to measure Distance, in a number of different systems including Imperial units United States However, for each of these units there exist two slightly different definitions, yielding two different systems of measure - international measure, and U. S. survey measure. The relationships between the different units within each measure is the same, but each measure has a slightly different definition in terms of metric units.

One inch international measure is exactly 25. 4 millimeters, while one inch U. S. survey measure is defined so that 39. 37 inches is exactly 1 meter. Inches redirects here To see the Les Savy Fav album see Inches. The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International For most applications, the difference is insignificant (about 3 millimeters per mile). International measure is used for everyday use, engineering, and commerce in the United States, while survey measure is used only for surveying.

International measure, agreed in 1959, uses the same definition of the units involved as is used in the UK and other Commonwealth countries. Before that date, those other countries still used separate standards. U. S. survey measure uses an older definition of the units (specified by the Mendenhall Order in 1893) which the United States used prior to adopting international measure. The Mendenhall Order marked a decision to change the fundamental standards of length and mass of the United States from the customary standards based on those of England to metric Previous to this agreement, the US standard was identical to survey measure.

UnitDivisionsSI Equivalent
Exact relationships shown in boldface
International
1 inch (in)25. Inches redirects here To see the Les Savy Fav album see Inches. 4 mm
1 foot (ft)12 in0. A foot (plural feet or foot; symbol or abbreviation ft or sometimes &prime – the prime symbol) is a non-SI unit 3048 m
1 yard (yd)3 ft0. A yard (abbreviation yd) is a unit of Length in several different systems including English units Imperial units and United 9144 m
1 mile (mi)5,280 ft1. A mile is a unit of Length, usually used to measure Distance, in a number of different systems including Imperial units United States 609344 km
Survey
1 link (li)3350 ft0. The link (usually abbreviated as "l" "li" or "lnk 201168 m
1 foot (survey)12003937 m0. A foot (plural feet or foot; symbol or abbreviation ft or sometimes &prime – the prime symbol) is a non-SI unit 3048006 m
1 rod (rd)25 li5. The rod is a unit of Length equal to 55 Yards 11 Cubits 50292 Meters 16 029210 m
1 chain (ch)4 rd20. A chain is a unit of Length; it measures 66 feet or 22 yards (20 1168 m
1 mile (survey)80 ch1. A mile is a unit of Length, usually used to measure Distance, in a number of different systems including Imperial units United States 609347 km

## Units of capacity and volume

The cubic inch, cubic foot and cubic yard are commonly used for measuring volume. A cubic inch (plural cubic inches) is a non- SI unit of Volume, equal to the volume of a Cube with sides of one Inch. The cubic foot is an imperial and US customary (non- metric) unit of Volume, used in the United States Canada and the United Kingdom A cubic yard is an Imperial / US customary (non- SI non- metric) unit of Volume, used in the United States, Canada and In addition, there is one group of units for measuring volumes of liquids, and one for measuring volumes of dry material.

Other than the cubic foot, cubic inch and cubic yard, these units are differently sized from the units in the Imperial system, although the names of the units are similar. Imperial units or the Imperial system is a collection of units first defined in the British Weights and Measures Act of 1824 Also, while the U. S. has separate systems for measuring the volumes of liquids and dry material, the Imperial system has one set of units for both.

Technically speaking, since these units are defined in terms of the inch, it would make a difference whether international or survey measure was used. However, in practice, the difference between the two definitions would be imperceptible, and in any case in defining volumes international measure is used.

### Volume in general

UnitDivisionsSI Equivalent
1 cubic inch (cu in)16. A cubic inch (plural cubic inches) is a non- SI unit of Volume, equal to the volume of a Cube with sides of one Inch. 387 064 mL[6]
1 cubic foot (cu ft)1 728 cu in28. The cubic foot is an imperial and US customary (non- metric) unit of Volume, used in the United States Canada and the United Kingdom 316 846 592 L
1 cubic yard (cu yd)27 cu ft764. A cubic yard is an Imperial / US customary (non- SI non- metric) unit of Volume, used in the United States, Canada and 554 857 984 L
or
0. 764 554 857 984 m³

### Liquid volume

Most important measures shown in bold font

UnitDivisionsSI Equivalent
1 minim (min)0. The minim (abbreviated min or ♏) is a unit of Volume in both the imperial and US customary systems of measurement 061 611 52 mL
1 fluid dram (fl dr)60 min3. The dram (archaic spelling drachm; Apothecary symbol ℨ) was historically both a Coin and a Weight. 696 691 mL
1 fluid ounce (fl oz)8 fl dr29. A fluid ounce (abbreviated fl oz, fl oz or oz fl) is a unit of Volume in both the imperial and the US customary systems 573 53 mL
1 gill (gi)4 fl oz118. The litre or liter (see spelling differences) is a unit of Volume. The gill (ˈdʒɪl Homophone of " Jill " is a Unit of measurement for volume equal to a quarter of a Pint. 294 1 mL
1 cup (cp) or (c)2 gi or 8 fl oz236. The cup is a unit of measurement for volume used in cooking to measure bulk foods such as Granulated sugar (dry measurement and liquids ( Fluid measurement A fluid ounce (abbreviated fl oz, fl oz or oz fl) is a unit of Volume in both the imperial and the US customary systems 588 2 mL
1 (liquid) pint (pt)2 cups or 4 gi or 16 fl oz473. The pint is an English unit of Volume or capacity in the imperial system and United States customary units. 176 5 mL
1 (liquid) quart (qt)2 pt or 32 fl oz946. The quart is an imperial and US customary unit of Volume equal to a quarter of a Gallon. 352 9 mL
1 gallon (gal)4 qt or 128 fl oz or 231 cu in3. A gallon is a measure of Volume. It is in current use in the United States and still has limited use in many other English-speaking countries A cubic inch (plural cubic inches) is a non- SI unit of Volume, equal to the volume of a Cube with sides of one Inch. 785 412 L
1 beer barrel (bbl)31 gal117. 347 8 L
1 oil barrel (bbl)42 gal158. 987 3 L
1 hogshead63 gal238. A hogshead is a large cask of liquid (less often of a food commodity) 481 0 L

The gill—pronounced /ˈdʒɪl/—is basically a paper unit which is not actually used in the United States any more. Minims and drams are also rarely used. Single servings of beverages are usually measured in fluid ounces. Milk is usually sold in cups or half pints (8 fluid ounces), pints, quarts and gallons. Water volume for sinks, bathtubs, ponds, swimming pools, etc. , is usually described in gallons. The fluid ounce derives its name originally from being the volume of one ounce avoirdupois of water, but in the US it is defined as the 128th part of a US gallon, so a fluid ounce of water weighs about 1. The avoirdupois (ˌævərdəˈpɔɪz French avwaʀdypwɑ system is a system of weights (or properly Mass) based on a pound of sixteen Ounces 043 ounces. The saying "a pint's a pound the world around" refers to 16 fluid ounces being one pint in the United States, but ironically it is only approximately true in the US. In the rest of the English-speaking world 20 fluid ounces make a pint, so it is said that "A pint of water weighs a pound and a quarter".

### Dry volume

UnitDivisionsSI Equivalent
1 (dry) pint (pt)33. The pint is an English unit of Volume or capacity in the imperial system and United States customary units. 6003125 cu in (exactly)550. 610 5 mL
1 (dry) quart (qt)2 pt1. The quart is an imperial and US customary unit of Volume equal to a quarter of a Gallon. 101 221 L
1 (dry) gallon4 qt4. 404 884 L
1 peck (pk)2 (dry) gallons8. A peck is an imperial and US customary unit of dry volume, equivalent in each of these systems to 8 dry Quarts or 16 dry Pints Two 809 768 L
1 bushel (bu)4 pk35. A bushel is a unit of dry volume, usually subdivided into eight local Gallons in the systems of Imperial units and U 239 07 L

Small fruits, berries, and vegetables are often sold in dry pints and dry quarts. Most Americans do not have experience with dry gallons, however pecks, or bushels are sometimes used particularly for apples and similar fruits in agricultural regions. A peck is an imperial and US customary unit of dry volume, equivalent in each of these systems to 8 dry Quarts or 16 dry Pints Two A bushel is a unit of dry volume, usually subdivided into eight local Gallons in the systems of Imperial units and U

## Units of mass

There have historically been four different English systems of mass: Tower weight, Troy weight, Avoirdupois system, and Apothecaries' system. The pound or pound-mass (abbreviation lb, lbm, or sometimes in the United States #) is a unit of Mass Troy weight is a system of units of Mass customarily used for Precious metals Black powder, and Gemstones Named after Troyes The avoirdupois (ˌævərdəˈpɔɪz French avwaʀdypwɑ system is a system of weights (or properly Mass) based on a pound of sixteen Ounces Tower weight fell out of use (due to legal prohibition) centuries ago, and was never used in the United States. Troy weight is still used to weigh precious metals. Apothecaries weight, once used in pharmacy, has been largely replaced by metric measurements. Avoirdupois mass, being directly related to the kilogram, is used to define mass in the U. S. customary system today.

The Avoirdupois pound is legally defined as a measure of mass, but the name pound is also applied to measures of force. Mass is a fundamental concept in Physics, roughly corresponding to the Intuitive idea of how much Matter there is in an object In Physics, a force is whatever can cause an object with Mass to Accelerate. For instance, in many contexts, the pound avoirdupois is used as a unit of mass, but in the some contexts, the term "pound" is almost exclusively used to refer to "pound-force". The pound or pound-mass (abbreviation lb, lbm, or sometimes in the United States #) is a unit of Mass This article deals with the unit of force For the unit of mass see Pound (mass.

Troy weight, avoirdupois weight, and apothecaries weight are all defined in terms of the same basic unit, the grain, which is the same in all three systems. However, while each system has some overlap in the names of their units of measure (all have ounces and pounds), the relationship between the grain and these other units within each system varies. For example, in apothecaries and troy weight, the pound and ounce are the same, but are different from the pound and ounce in avoirdupois, in terms of their relationships to grains and to each other. The systems also have different units between the grain and ounce (apothecaries has scruple and dram, troy has pennyweight, and avoirdupois has just dram). The dram was once known as the drachm.

To alleviate confusion, it is typical when publishing non-avoirdupois weights to mention the name of the system along with the unit. Precious metals, for example, are often weighed in "troy ounces", because just "ounce" would be more likely to be assumed to mean an ounce avoirdupois.

The pound avoirdupois, which forms the basis of the U. S. customary system of mass, is defined as exactly 453. 59237 grams. For other uses of the words gram or gramme see Gram (disambiguation. All the other units of mass are defined in terms of it.

For the pound and smaller units, the U. S. customary system and the British Imperial system are identical. However, they differ when dealing with units larger than the pound. The definition of the pound avoirdupois in the British Imperial system is identical to that in the U. S. customary system.

### Avoirdupois weight

Main article: Avoirdupois
UnitDivisionsSI Equivalent
1 grain (gr)17000 lb64. The avoirdupois (ˌævərdəˈpɔɪz French avwaʀdypwɑ system is a system of weights (or properly Mass) based on a pound of sixteen Ounces In many cultures a grain is a unit of measurement of Mass that is based upon the mass of a single seed of a typical Cereal. 798 91 mg
1 dram (dr)271132 gr1. 771 845 195 312 5 g
1 ounce (oz)16 dr28. This article is about the unit of mass For the unit of force see Pound-force. 349 523 125 g
1 pound (lb)16 oz453. The pound or pound-mass (abbreviation lb, lbm, or sometimes in the United States #) is a unit of Mass 592 37 g
1 hundredweight (cwt)100 lb45. Hundred weight or hundredweight is a Unit of measurement for Mass in U 359 237 kg
1 (short) ton20 cwt907. The short ton ( S/T) is a unit of mass equal to 2000 lb (around 907 184 74 kg

In the United States, only the ounce, pound and short ton — known in the country simply as the ton — are commonly used, though the hundredweight is still used in agriculture and shipping.

### Troy weight

Main article: Troy weight

The grain has the same definition as for Avoirdupois weight. Troy weight is a system of units of Mass customarily used for Precious metals Black powder, and Gemstones Named after Troyes

UnitDivisionsSI Equivalent
1 pennyweight (dwt)24 gr1. A pennyweight (dwt is a unit of Mass which is the same as 24 grains, 1/240th of a Troy pound, 1/20th of a Troy ounce, approximately 0 555 173 84 g
1 troy ounce (oz t)20 dwt31. Troy weight is a system of units of Mass customarily used for Precious metals Black powder, and Gemstones Named after Troyes 103 476 8 g
1 troy pound (lb t)12 oz t373. Troy weight is a system of units of Mass customarily used for Precious metals Black powder, and Gemstones Named after Troyes 241 721 6 g

## Cooking measures

The most common cooking weights and measures in the United States are as follows:

UnitDivisionsSI Equivalent
1 teaspoon (tsp)5 mL
1 tablespoon (tbsp)3 tsp15 mL
1 cup16 tbsp240 mL
1 stick4 oz115 g

The SI equivalents have been rounded to reasonable values in the table above, because cooking is not a precise science. In Recipes quantities of ingredients may be specified by Mass ("weight" by Volume, or by count. A teaspoon is a small Spoon, or a spoon used in measuring commonly used to stir the contents of a cup of Tea or Coffee. A tablespoon is a type of Spoon used for serving Measure of volume It is also a measure of Volume used in cooking The cup is a unit of measurement for volume used in cooking to measure bulk foods such as Granulated sugar (dry measurement and liquids ( Fluid measurement

## Grain measures

In agricultural practice, a bushel is a fixed mass of grain, nominally based on dry volume units. A bushel is a unit of dry volume, usually subdivided into eight local Gallons in the systems of Imperial units and U

• 1 bushel (maize) = 56 lb ≈ 25. 401 kg
• 1 bushel (wheat) = 60 lb ≈ 27. 216 kg

## Units of temperature

Degrees Fahrenheit are used in the United States to measure temperatures in most non-scientific contexts. Fahrenheit is a temperature scale named after Daniel Gabriel Fahrenheit (1686–1736 a German Physicist who proposed it in 1724 Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature

• Pure water freezes at 32 °F and boils at 212 °F at 1 atm. The Standard atmosphere is an international reference pressure defined as 101325 Pa and formerly used as unit of Pressure (symbol atm
• Water saturated with common salt freezes at −6. 02 °F.
• Conversion formula: $F = \frac{9}{5}C + 32$
• For a rough conversion formula that is easier to perform in one's head, American travelers to regions that use Celsius may prefer $F \approx 2C + 30\,$ which is identical to the real formula when F=50 and is accurate to within 5 degrees Fahrenheit when $5 \le F \le 95$.

For scientific matters the Rankine scale, an absolute temperature scale based upon Fahrenheit, saw some use. Rankine is a thermodynamic (absolute temperature scale named after the Scottish Engineer and Physicist William John Macquorn Rankine Modern scientists almost always use the Kelvin and Celsius scales, though U. The kelvin (symbol K) is a unit increment of Temperature and is one of the seven SI base units The Kelvin scale is a thermodynamic The Celsius Temperature scale was previously known as the centigrade scale. S. medical practitioners often use the U. S. customary units for body temperature and weight.

## Other units

• British thermal unit (~ 1055 J)
• Horsepower (~ 746 W)
• Hand (10. See also Hand A hand (or handbreadth) is a unit of length Measurement, originally based on the breadth of a Male Human hand 16 cm)
• Calorie (4. This article is about the unit of energy For its use in Nutrition and Food labelling regulations, see the article on Food energy. 184 J or kJ, depending on usage)
• Board-foot (2. The board-foot is a specialized unit of Volume for measuring Lumber in the United States and Canada. 360 dm³)
• R-value (0. 176 K·m²/W)
• Slug (mass) (1 lbf·s²/ft)

## Notes

1. ^ "English units of measurement." (2001-2007). The slug is an English unit of Mass. It is a mass that accelerates by 1 ft/s² when a force of one Pound-force (lbf is exerted on it This article deals with the unit of force For the unit of mass see Pound (mass. The Columbia Encyclopedia 6th ed. Accessed at
2. ^ http://www.opsi.gov.uk/si/si1995/Uksi_19951804_en_1.htm Units of Measurement Regulations 1995, Statutory Instrument 1995 No. 1804
3. ^ a b Ed Tenner, (May 2005), "The Trouble with the Meter"
4. ^ Robyn Williams (February 8, 1998) Trouble with the Metric System Australian Radio National, Ockham's Razor. Events 421 - Constantius III becomes co- Emperor of the Western Roman Empire. Year 1998 ( MCMXCVIII) was a Common year starting on Thursday (link will display full 1998 Gregorian calendar) http://www.abc.net.au/rn/science/ockham/stories/s11563.htm
5. ^ “Appendix G - Weights and Measures”, The World Factbook, Washington: Central Intelligence Agency, 2007-01-17. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 38 BC - Octavian marries Livia Drusilla. 1287 - King Alfonso III of Aragon invades Minorca Retrieved on
6. ^ The liter should be abbreviated with a capital L per National Institute of Standards and Technology. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 211 - Roman Emperor Septimius Severus dies leaving the Roman Empire in the hands of his two quarrelsome sons (1995. ) Guide for the Use of the International System of Units (SI). Special Publication 811. http://physics.nist.gov/Pubs/SP811/sec06.html#6.1.2