Millimetre
millimetre | |
---|---|
SI | |
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 | 1×103 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 (
One millimetre is equal to 1000 micrometres or 1000000 nanometres. Since an inch is officially defined as exactly 25.4 millimetres, a millimetre is equal to exactly 5⁄127 (≈ 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.
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
- millimetre - U+339C ㎜ SQUARE MM
- square millimetre - U+339F ㎟ SQUARE MM SQUARED
- cubic millimetre U+33A3 ㎣ SQUARE MM CUBED
In Japanese typography, these square symbols are 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 rulers may be graduated in increments of 0.5 mm. Digital callipers are commonly capable of reading increments as small as 0.01 mm.[4]
The smallest dimension the human eye can resolve is around 0.02 to 0.04 mm, approximately the width of a thin
See also
References
- ^ "17th General Conference on Weights and Measures (1983), Resolution 1". International Bureau of Weights and Measures. Retrieved 3 December 2013.
- ^ "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.
- ISBN 9781118102756.
- ^ "How Small Can the Naked Eye See?". Focus Magazine. Retrieved 3 December 2013.
- ^ Sherlis, Juliya (2001). Elert, Glenn (ed.). "Thickness of a piece of paper". The Physics Factbook. Retrieved 2022-01-21.