{{short description|Unit of length}} {{broader|metre}} {{Use British English |date=February 2023}} {{Infobox unit | name = centimetre | image = frameless | caption = A carpenter's ruler with centimetre divisions | symbol = cm | standard = SI | quantity = length | units1 = millimetres | inunits1 = 10 mm | units2 = imperial & US system | inunits2 = ~{{convert|1|cm|in|4|disp=out|lk=out}} }} {{Wiktionary|centimetre}}

[[file:EM Spectrum Properties edit.svg|thumb|upright=1.35|Different lengths as in respect to the electromagnetic spectrum, measured by the metre and its derived scales. The microwave is in-between 1 metre to 1 millimetre.]]

A '''centimetre''' (International spelling) or '''centimeter''' (American English), with SI symbol '''cm''', is a unit of length in the International System of Units (SI) equal to one hundredth of a metre, ''centi-'' being the SI prefix for a factor of {{sfrac|100}}.<ref>{{cite web |url=http://www.bipm.org/en/publications/si-brochure/chapter3.html |title=Decimal multiples and submultiples of SI units |publisher=Bureau International des Poids et Mesures |year=2014 |access-date=5 July 2015}}</ref> Equivalently, there are 100 centimetres in 1 metre. The centimetre is the base unit of length in the now deprecated centimetre–gram–second (CGS) system of units.

Though for many physical quantities, SI prefixes for factors of 10<sup>3</sup>—like ''milli-'' and ''kilo-''—are often preferred by technicians, the centimetre remains a practical unit of length for many everyday measurements; for instance, human height is commonly measured in centimetres.<ref>{{cite web|title=Using the BMI-for-Age Growth Charts |url=https://www.cdc.gov/nccdphp/dnpa/growthcharts/training/modules/module1/text/page6bmetric.htm |website=cdc.gov |publisher=Centers for Disease Control |access-date=5 July 2014 |url-status=dead |archive-url=https://web.archive.org/web/20140130012800/http://www.cdc.gov/nccdphp/dnpa/growthcharts/training/modules/module1/text/page6bmetric.htm |archive-date=30 January 2014 |df=dmy }}</ref><ref>{{cite book|author=Price, Beth|title=MathsWorld Year 8 VELS Edition|date=2009|publisher=MacMillan|location=Australia|page=626|url=https://books.google.com/books?id=t2veDRPjMggC|display-authors=etal|isbn=978-0-7329-9251-4}}</ref> A centimetre is approximately the width of the fingernail of an average adult person.

==Equivalence to other units of length==

{| |- |rowspan=4 valign=top|{{calculator|id=cm|type=number|size=4|default=1}} centimetre |= {{calculator|id=mm|type=plain|default=10|formula=cm*10|NaN-text=0}} millimetres |- |= {{calculator|id=m|type=plain|default=0.01|formula=cm/100|NaN-text=0}} metres |- |= {{calculator|id=in|type=plain|default=0.3937|formula=cm/2.54|NaN-text=0|decimals=4}} inches (There are ''exactly'' 2.54 centimetres in one inch.) |}

One millilitre is defined as one cubic centimetre, under the SI system of units.

==Other uses== In addition to its use in the measurement of length, the centimetre is used: * sometimes, to report the level of rainfall as measured by a rain gauge<ref>{{Cite web|url=https://www.weathershack.com/static/ed-rain-measurement.html|title=Rain Measurement|website=www.weathershack.com}}</ref> * in the CGS system, the centimetre is used to measure capacitance, where 1&nbsp;cm of capacitance = {{val|1.113|e=-12}} farads<ref>{{Cite web|url=https://scienceworld.wolfram.com/physics/Capacitance.html|title=Capacitance -- from Eric Weisstein's World of Physics|first=Eric W.|last=Weisstein|website=scienceworld.wolfram.com}}</ref> * in maps, centimetres are used to make conversions from map scale to real world scale (kilometres) * to represent second moment of areas (cm<sup>4</sup>) * as the inverse of the Kayser, a CGS unit, and thus a non-SI metric unit of wavenumber: 1 kayser = 1 wave per centimetre; or, more generally, (wavenumber in kaysers) = 1/(wavelength in centimetres). The SI unit of wavenumber is the inverse metre, m<sup>−1</sup>.

==Unicode symbols== For the purposes of compatibility with Chinese, Japanese and Korean (CJK) characters, Unicode has symbols for:<ref>[https://www.unicode.org/charts/PDF/U3300.pdf CJK Compatibility excerpt] from The Unicode Standard, Version 10.0.</ref> * centimetre – {{unichar|339D|SQUARE CM}} * square centimetre – {{unichar|33A0|SQUARE CM SQUARED}} * cubic centimetre – {{unichar|33A4|SQUARE CM CUBED}}

These characters are each equal in size to one Chinese character and are typically used only with East Asian, fixed-width CJK fonts.

==See also== *Conversion of units *Orders of magnitude (length) *Reciprocal length

==References== {{reflist}}

==External links== * [https://stylespree.com/pages/cm-to-inch-converter CM to Inch Converter]

{{SI units of length}} {{CGS units}}

{{Authority control}}

Category:Metre -02 Category:Centimetre–gram–second system of units Category:SI units Category:100 (number) Category:Units of length