Micrometre
| Micrometre | |
|---|---|
a 6 μm diameter carbon filament,
compared to 50 μm diameter human hair |
|
| Unit system | metric |
| Unit of | length |
| Symbol | μm |
| 1 μm in ... | ... is equal to ... |
| SI units | 1×10−6 m |
| Natural units |
6.1877×1028 ℓP 1.8897×104 a0 |
| imperial/US units |
3.2808×10−6 ft 3.9370×10−5 in |
The micrometre (International spelling as used by the International Bureau of Weights and Measures;SI symbol: μm) or micrometer (American spelling), also commonly known as a micron, is an SI derived unit of length equaling 1×10−6 of a 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 0.000039 inch). The symbol μm is sometimes rendered as um if the symbol μ cannot be used, or if the writer is not aware of the distinction.
The micrometre is a common unit of measurement for wavelengths of infrared radiation as well as sizes of biological cells and bacteria and is also commonly used in plastics manufacturing. Micrometres are the standard for grading wool by the diameter of the fibres; wool finer than 25 μm can be used for garments, while coarser grades are used for outerwear, rugs, and carpets. The width of a single human hair ranges from approximately 10 to 200 μm. The first and longest human chromosome is 10μm in length.
Between 1 μm and 10 μm:
Between 10 μm and 100 μm
The term micron and the symbol μ were officially accepted for use in isolation to denote the micrometre in 1879, but officially revoked by the International System of Units (SI) in 1967. This was necessary because that older usage became incompatible with the official adoption of the unit prefix micro-, denoted μ, during the creation of the SI in 1960. In the SI, the systematic name micrometre became the official name of the unit, and μm became the official unit symbol.
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