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Millimetre

Unit of length 1/1000 of a metre

Field	Value
name	millimetre
image	Ruler with millimeter and centimeter marks.png
caption	Ruler with millimetre and centimetre marks
standard	SI
quantity	Length
symbol	mm
namedafter	From metric prefix mille (Latin for "one thousand") and the metre
units1	micrometres
inunits1	1000
units2	centimetres
inunits2
units3	metres
inunits3
units4	kilometres
inunits4
units5	decimetres
inunits5
units6	inches
inunits6	1 mm
units7	feet
inunits7	1 mm

The millimetre (SI symbol: mm; international spelling) or millimeter (American spelling) is a unit of length in the International System of Units (SI), equal to one thousandth of a metre, the SI base unit of length.

1 metre = 1000 millimetres
1 centimetre = 10 millimetres

One millimetre is also equal to:

micrometres
nanometres

Since an inch is officially defined as exactly 25.4 millimetres, 1 millimetre is precisely inches (≈ 0.03937 inches).

Definition

Since 1983, the metre has been defined as "the length of the path travelled by light in vacuum during a time interval of of a second".

A millimetre, being of a metre, is the distance light travels in of a second.

Informal terminology

The term "mil" is sometimes used colloquially for millimetre. However, in the United States, "mil" traditionally means a thousandth of an inch, which may cause confusion.

Unicode symbols

To support layout compatibility with East Asian scripts (CJK), Unicode includes square symbols for:

Millimetre –
Square millimetre –
Cubic millimetre –

These symbols are often used in Japanese typography to align unit symbols with text characters.

Measurement

On a standard metric ruler, the smallest divisions are typically millimetres.
Precision engineering rulers may show increments of 0.5 mm.
Digital calipers often measure to 0.01 mm accuracy.

Examples:

Microwaves with a frequency of 300 GHz have a wavelength of 1 mm.
Using frequencies from 30–300 GHz for millimetre-wave communications allows high-speed data transfer (e.g., 10 Gbps).
The smallest visible object to the human eye is around 0.02–0.04 mm (e.g., a thin human hair).
A typical sheet of paper is between 0.07 mm and 0.18 mm thick; copy paper is about 0.1 mm.

References

"17th General Conference on Weights and Measures (1983), Resolution 1.". International Bureau of Weights and Measures.
"CJK Compatibility". unicode.org.
"How do I read a ruler?". onlineconversion.com.
"Accuracy of Calipers". TresnaInstrument.com.
(2011). "Millimeter Wave Communication Systems". John Wiley & Sons.
"How Small Can the Naked Eye See?". Focus Magazine.
Sherlis, Juliya. (2001). "Thickness of a piece of paper".

Info: Wikipedia Source

This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page.

metre orders-of-magnitude-(length) 1000-(number) units-of-length

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