Millimetre
| Millimetre | |
|---|---|
 Ruler with millimetre and centimetre marks | |
| General information | |
| Unit system | SI derived unit |
| Unit of | Length |
| Symbol | mm |
| Named after | The metric prefix mille (Latin for "one thousand") and the metre |
| Conversions | |
| 1 mm in ... | ... is equal to ... |
micrometres | 6997100000000000000♠1×103 μm = 1000 μm |
centimetres | 6999100000000000000♠1×10−1 cm = 0.1 cm |
metres | 6997100000000000000♠1×10−3 m = 0.001 m |
kilometres | 6997100000000000000♠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 7003100000000000000♠1000 micrometres or 7006100000000000000♠1000000 nanometres. A millimetre is equal to exactly 5⁄127 (approximately 0.039370) of an inch.
Contents
1 Definition
2 Informal Terminology
3 Unicode symbols
4 Measurement
5 See also
6 References
Definition
Since 1983, the metre has been defined as "the length of the path travelled by light in vacuum during a time interval of 1/7008299792458000000♠299792458 of a second".[1] A millimetre, 1/1000 of a metre, is therefore the distance travelled by light in 1/7011299792458000000♠299792458000 of a second.
Informal Terminology
A common shortening of millimetre in spoken English is "mil". This can cause confusion since in the United States, "mil" traditionally means a thousandth of an inch.
Unicode symbols
For the purposes of compatibility with Chinese, Japanese and Korean (CJK) characters, Unicode has symbols for:
- millimetre (㎜) - code U+339C[2]
- square millimetre (㎟) - code U+339F[2]
- cubic millimetre (㎣) - code U+33A3[2]
In Japanese typography, these square symbols were historically used for laying out unit symbols without distorting the grid layout of text characters.
Measurement
On a metric ruler, the smallest measurements are normally millimetres.[3] High-quality engineering rules may be graduated in increments of 0.5 mm. Digital callipers are commonly capable of reading increments as small as 0.01 mm.[4]
Microwaves with a frequency of 300 GHz have a wavelength of 1 mm. Using wavelengths between 30 GHz and 300 GHz for data transmission, in contrast to the 300 MHz to 3 GHz normally used in mobile devices, has the potential to allow data transfer rates of 10 gigabits per second.[5]
The smallest distances the human eye can resolve is around 0.02 to 0.04 mm, approximately the width of a human hair.[6] A sheet of paper is typically between 0.07 mm and 0.18 mm thick, with ordinary printer paper or copy paper approximately a tenth of a millimetre thick.[7]
See also
 | Look up millimetre in Wiktionary, the free dictionary. |
- Metric system
- Orders of magnitude (length)
- Submillimeter
References
^ "17th General Conference on Weights and Measures (1983), Resolution 1". International Bureau of Weights and Measures. Retrieved 3 December 2013..mw-parser-output cite.citation{font-style:inherit}.mw-parser-output .citation q{quotes:"""""""'""'"}.mw-parser-output .citation .cs1-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Lock-green.svg/9px-Lock-green.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .citation .cs1-lock-limited a,.mw-parser-output .citation .cs1-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Lock-gray-alt-2.svg/9px-Lock-gray-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .citation .cs1-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Lock-red-alt-2.svg/9px-Lock-red-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/4/4c/Wikisource-logo.svg/12px-Wikisource-logo.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{font-size:100%}.mw-parser-output .cs1-maint{display:none;color:#33aa33;margin-left:0.3em}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em}
^ abc "CJK Compatibility" (PDF). unicode.org. Retrieved 3 December 2013.
^ "How do I read a ruler?". onlineconversion.com. Retrieved 3 December 2013.
^ "Accuracy of Calipers". TresnaInstrument.com. Retrieved 3 December 2013.
^ Huang, Kao-Cheng; Wang, Zhaocheng (2011). Millimeter Wave Communication Systems. ISBN 9781118102756.
^ "How Small Can the Naked Eye See?". Focus Magazine. Retrieved 3 December 2013.
^ "Thickness of a Piece of Paper". hypertextbook.com. Retrieved 3 December 2013.
