micrometre | |
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![]() A 6 μm diameter carbon filament above a 50 μm diameter human hair | |
General information | |
Unit system | SI |
Unit of | length |
Symbol | μm |
Conversions | |
1 μm in ... | ... is equal to ... |
SI base units | 10−6 m |
Natural units | 1.8897×104 a0 |
imperial/US units | 3.9370×10−5 in |
The micrometre (Commonwealth English) as used by the International Bureau of Weights and Measures;[1] SI symbol: μm) or micrometer (American English), also commonly known by the non-SI term micron,[2] is a unit of length in the International System of Units (SI) equalling 1×10−6 metre (SI standard prefix "micro-" = 10−6); that is, one millionth of a metre (or one thousandth of a millimetre, 0.001 mm, or about 0.00004 inch).[1]
The nearest smaller common SI unit is the nanometre, equivalent to one thousandth of a micrometre, one millionth of a millimetre or one billionth of a metre (0.000000001 m).
The micrometre is a common unit of measurement for wavelengths of infrared radiation as well as sizes of biological cells and bacteria,[1] and for grading wool by the diameter of the fibres.[3] The width of a single human hair ranges from approximately 20 to 200 μm.