View source for Unit of measurement

You do not have permission to edit this page, for the following reason:

You currently can not change pages on Wikipedia.

The ability to change pages on all Wikimedia wikis has been removed from this account, IP address or IP address range by ‪AntiCompositeNumber‬. The following reason(s) were given for this block:

Open proxy/Webhost: Visit the FAQ if you are affected

Your IP address is 44.201.58.159. This block began on 13:55, 18 August 2022 and has been set to finish on: 13:55, 18 April 2025.

You are not blocked from reading pages, only from changing or creating them.
If you have just clicked a red link, you were blocked from creating a new page as no article on that topic is there yet.

If you think you were not blocked fairly, you may make unblock requests or file appeals at meta:Steward requests/Global.

You can view and copy the source of this page.

[[File:CubeLitre.svg|thumb|This cube can hold one [[litre]] of a [[liquid]]]]
[[File:Masskrug.jpg|thumb|Beer mugs, at [[Oktoberfest]]: They hold one litre of beer]]

'''Units of measurement''' give ''[[standard]]s'' so that the numbers from our measurements refer to the same thing. [[Measurement]] is a process that uses [[number]]s to describe a [[physical quantity]]. We can measure how big things are, how warm they are, how heavy they are, and many other features.

For example, the [[metre]] is a standard unit to measure [[length]]. Before 1982, one meter was defined as the distance between two markers on a special metal rod. During that time, saying that something had a length of two meters meant that it was exactly twice as long as the rod used to define the meter. Now scientists define the meter by using the [[speed of light]].

In the past, different units were used in different countries. Today, most units of measure fall into one of three [[System of measurement|systems]]:

The older two, the [[Imperial units|British imperial system]] and the closely related [[United States customary units|US customary system]] use the [[Foot (unit of length)|foot]] as a measure of length, the [[Pound (mass)|pound]] as a measure for [[weight]], and the [[second]] as a measure for time. They use other units as well. The number of smaller units that make the bigger units in these two systems varies: For example, there are 12 [[inch]]es in a foot and 16 [[ounce]]s in a pound. 

The newest and most used of the three systems is the [[metric system]] or [[SI units|SI system]] which use 10, 100 or 1000 of a smaller unit to make a bigger one. For instance, there are 100 centimetres in one metre or 1000 grams in one kilogram. This system uses the metre for length and [[kilogram]] for mass. 

The common, non-metric measurement of [[time]] does not follow this pattern. The [[second]] is the basis for time measurement, and it is based on the [[sexagesimal]] system: 60 seconds make one [[minute]], and 60 minutes make one [[hour]].

== Number and unit of measurement ==
The property of the thing being measured is given as a [[number]] of units of measure. The number only has [[sense]] when the unit of measurement is also given. By that number it represents a measurement of something.

For example, [[Eiffel Tower|The Eiffel Tower]] in [[Paris]], [[France]] is {{convert|300|m|abbr=off}} [[height|tall]].<ref>A person can also say "The Eiffel Tower's [[height]] is 300 metres".</ref>  That is, the [[distance]] from the top to the bottom of the Eiffel Tower is 300 metres.  The property of the Eiffel Tower being measured is a distance.  The number measured is 300.  300 of what?  The unit of measurement is the metre.

== Measurement standards ==
[[Standard]]s are usually special objects used to make measurements.  A metre stick is an example of a standard.  When you measure something with a metre stick, you can compare that measurement to anything else that is also measured with a metre stick. This makes measurement easier and [[wikt:comparison|comparisons]] between measurements easier.

[[Science]], [[medicine]] and [[engineering]] use smaller units of measurement to measure small things with less [[error]]. It is [[easy]] to measure large things using larger units of measurement.  [[Astronomical]] measurements like the [[width]] of a [[galaxy]] use [[light year]]s and [[parsec]]s.

Small measurements like the [[Atomic mass|mass of an atom]] use special units of measurement.

== Systems of units of measurement ==
{{Main article| System of measurement}}

There are many different standards and units used all over the world. Some became less used during the 19th and 20th centuries.

[[File:Metric_and_imperial_systems_(2019).svg|thumb|upright=1.35|Countries using the [[Metric system|metric]], [[Imperial units|imperial]], and [[United States customary units|US customary]] systems as of 2019]]

===Metric System===
{{main|International System of Units|Metric system}}

The [[metric system]] is a system of measurement used in most of the world. It is also called the International System of Units, or [[SI]].

Units of measure in the metric system include:

*The units of [[length]] or [[linear size]] are based on the [[metre]]. They include the [[kilometre]] (''km'') which is 1,000 metres, the [[centimetre]] (''cm''), and the [[millimetre]] (''mm'') which is 1/1,000th of a metre.

*The unit of [[volume]] is the [[litre]]. It is used for measuring an amount of [[liquid]].  A [[millilitre]] ([[abbreviate]]d as ''mL'') is the amount of liquid that would fill up a [[cube]] that measures 1 centimetre on each side. One litre of liquid would fill up a [[cube]] that is 10&nbsp;cm on each side.

*The unit of [[mass]] is the [[kilogram]].  A kilogram (''kg'') is the mass of 1 litre of water (at {{cvt|4|°C|disp=or|lk=on}} temperature and {{cvt|1013.25|kPa|disp=or|lk=on}} pressure). 1 gram (''g'') is the mass of 1 millilitre of [[water]] at {{cvt|4|°C}}.  The metric [[tonne]] is 1,000 kilograms or a [[million]] grams.

===Imperial units===
{{main|Imperial units}}
Imperial units were defined in the United Kingdom in 1824. These units were based on similar units that were in use before 1824. Imperial units were used in countries that were part of the [[British Empire]]. While many of these countries, including the United Kingdom, have officially adopted SI, the older system of units are still used.

===US customary units===
{{main|United States customary units}}
US customary units are the official units used in the US. These are similar to the British imperial units and also based on the units used in the United Kingdom from before [[American Revolution|American Independence]]. Some of the units are different to the British ones. For example, there are 20 imperial fluid ounces in an imperial pint, but 16 US fluid ounces in a US pint. Additionally, the US fluid ounce is slightly bigger than the imperial fluid ounce. The result is that US pints and gallons are smaller than imperial pints and gallons. In the United States, the metric system has been legal for trade since 1866 but other measurements such as the gallon, inch, and the pound are still widely used.

Imperial and US units of measurement include:
*Length - [[inch]] (''in''), [[Foot (unit of length)|foot]] (''ft''), [[yard]] (''yd''), and [[mile]].
**1 foot = 12 inches
**1 yard = 3 feet (plural of foot) = 36 inches
**1 mile = 1760 yards = 5280 feet

*Imperial volume - [[imperial fluid ounce]] (''fl oz''), [[imperial pint]] (''pt''), and [[imperial gallon]] (''gal'').
**1 imperial pint = 20 imperial fluid ounces
**1 imperial gallon = 8 imperial pints

*US volume - [[US fluid ounce]] (''fl oz''), US cup (''cp''), [[US pint]] (''pt''), [[US quart]] (''qt''), and [[US gallon]] (''gal'').
**1 US cup = 8 US fluid ounces
**1 US pint = 2 US cups = 16 US fluid ounces
**1 US quart = 2 US pints = 4 US cups = 32 US fluid ounces
**1 US gallon = 4 US quarts = 8 US pints = 16 US cups

*[[Weight]] and [[mass]] - ounce (''oz''), pound (''lb''), and [[stone (unit)|stone]] (''st'').
**1 pound = 16 ounces
**1 stone = 14 pounds

The ounces for weight and volume are different. Even when measuring [[water]], the number of ounces of weight is not the same as the number of fluid ounces.

===Converting between systems===
;Metric to US
*1 metre = 1.09 yards = 39.37 inches.
*1 [[litre]] = 33.3 fluid ounces = 1.76 pints = .26 US gallons.
*1 kilogram = 35.32 ounces = 2.2 pounds

;US to metric
*Length
**1 inch = 2.54 centimetres
**1 foot = 30.48 centimetres
**1 yard = 0.9144 metres
**1 mile = 1.609344 kilometres
*Volume
**1 fluid ounce = 29.6 millilitres
**1 pint = 473.1 millilitres
**1 gallon = 3.79 litres
**1 cup = 236.55 millilitres
*Mass
**1 ounce = 28.35 grams
**1 pound = 0.45359237 kilograms

== Other units of measurement ==
The unit of [[time]] is the [[second]]. The [[minute]] (60 seconds) and [[hour]] (60 minutes or 3600 seconds) are larger units. A [[day]] is defined as 24 hours, but the Earth’s rotation has slowed.  The difference is corrected at the end of some [[year]]s with what is called a leap second. A [[week]] (7 days) and [[month]] are also standard units.

A unit of measurement that applies to [[money]] is called a [[unit of account]].  This is normally a [[currency]] issued by a [[country]]. For instance, the [[United States]] use [[U.S. Dollar|dollars]]. Each dollar is 100 cents. The [[United Kingdom]] uses [[British pound|pounds]]. Each pound is 100 pennies or [[pence]]. The [[European Union]] uses the [[Euro]]. There are 100 cents in the Euro.

The units for [[electricity]], [[magnetism]] and [[radiation]] were mostly invented in the 19th century when scientists learned how to measure them. Most were originally given imperial systems, but it is usual to use metric systems for them today.<ref>* Rowlett, Russ (2005) [http://www.unc.edu/~rowlett/units/ A Dictionary of Units of Measurement] {{Webarchive|url=https://web.archive.org/web/20181010153750/http://www.unc.edu/~rowlett/units/ |date=2018-10-10 }} – Russ Rowlett and the University of North Carolina at Chapel Hill</ref>

== References ==
{{reflist}}


[[Category:Units of measurement| ]]

Templates used on this page:

Template:Convert (view source) (protected)
Template:Cvt (change)
Template:Main (view source) (semi-protected)
Template:Main article (change)
Template:Main other (view source) (protected)
Template:Reflist (view source) (protected)
Template:Reflist/styles.css (view source) (protected)
Template:Webarchive (view source) (protected)
Module:Arguments (view source) (protected)
Module:Check for unknown parameters (view source) (protected)
Module:Convert (view source) (protected)
Module:Convert/data (view source) (protected)
Module:Convert/text (view source) (protected)
Module:Format link (view source) (semi-protected)
Module:Hatnote (view source) (semi-protected)
Module:Hatnote/styles.css (view source) (semi-protected)
Module:Hatnote list (view source) (semi-protected)
Module:Labelled list hatnote (change)
Module:Webarchive (view source) (semi-protected)
Module:Webarchive/data (view source) (semi-protected)
Module:Yesno (view source) (protected)

Return to Unit of measurement

Retrieved from "https://simple.wikipedia.org/wiki/Unit_of_measurement"