# Millimetre

Millimetre
Ruler with millimetre and centimetre marks
General information
Unit systemSI derived unit
Unit ofLength
Symbolmm
Named afterThe metric prefix mille (Latin for "one thousand") and the metre
Conversions
1 mm in ...... is equal to ...
micrometres   1×103 μm = 1000 μm
centimetres   1×10−1 cm = 0.1 cm
metres   1×10−3 m = 0.001 m
kilometres   1×10−6 km
inches   0.039370 in
feet   0.0032808 ft

The millimetre (international spelling as used by the International Bureau of Weights and Measures; SI unit symbol mm) or millimeter (American spelling) is a unit of length in the metric system, equal to one thousandth of a metre, which is the SI base unit of length. Therefore, there are one thousand millimetres in a metre. There are ten millimetres in a centimetre.

One millimetre is equal to 1000 micrometres or 1000000 nanometres.Since an inch is officially defined as exactly 25.4 millimetres, a millimetre is therfore equal to exactly ​5127 (≈ 0.03937) of an inch.

## Definition

Since 1983, the metre has been defined as "the length of the path travelled by light in vacuum during a time interval of 1/299792458 of a second".[1] A millimetre, 1/1000 of a metre, is therefore the distance travelled by light in 1/299792458000 of a second.

Other Languages
Afrikaans: Millimeter
العربية: مليمتر
aragonés: Milimetro
asturianu: Milímetru
azərbaycanca: Millimetr
беларуская: Міліметр
беларуская (тарашкевіца)‎: Мілімэтар
български: Милиметър
bosanski: Milimetar
català: Mil·límetre
Чӑвашла: Миллиметр
čeština: Milimetr
Cymraeg: Milimetr
dansk: Millimeter
Deutsch: Millimeter
Ελληνικά: Χιλιοστόμετρο
emiliàn e rumagnòl: Milìmeter
español: Milímetro
Esperanto: Milimetro
euskara: Milimetro
فارسی: میلی‌متر
français: Millimètre
Frysk: Milimeter
furlan: Milimetri
galego: Milímetro

한국어: 밀리미터
հայերեն: Միլիմետր
हिन्दी: मिलीमीटर
Bahasa Indonesia: Milimeter
interlingua: Millimetro
íslenska: Millimetri
italiano: Millimetro
עברית: מילימטר
ქართული: მილიმეტრი
қазақша: Миллиметр
Kiswahili: Milimita
kurdî: Milîmetre
Latina: Millimetrum
latviešu: Milimetrs
Limburgs: Millimeter
македонски: Милиметар
मराठी: मिलीमीटर
მარგალური: მილიმეტრა
Mìng-dĕ̤ng-ngṳ̄: Hò̤-mī
Nederlands: Millimeter
norsk: Millimeter
norsk nynorsk: Millimeter
oʻzbekcha/ўзбекча: Millimetr
پنجابی: ملی میٹر
polski: Milimetr
português: Milímetro
русский: Миллиметр
Scots: Millimetre
shqip: Milimetri
sicilianu: Millìmitru
Simple English: Millimetre
slovenčina: Milimeter
slovenščina: Milimeter
Soomaaliga: Millimeter
کوردی: میلیمەتر
српски / srpski: Milimetar
srpskohrvatski / српскохрватски: Milimetar
svenska: Millimeter
Türkçe: Milimetre
українська: Міліметр
اردو: ملی میٹر
vèneto: Miłimetro
Tiếng Việt: Milimét
Winaray: Milimetro