This became necessary because the older usage was incompatible with the official adoption of the unit prefix micro-, denoted μ, during the creation of the SI in 1960. 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. The longest human chromosome is approximately 10 μm in length.įor more examples of things measuring 10 to 100 micrometres, see Orders of magnitude (length) § 10 micrometres. The width of a single human hair ranges from approximately 20 to 200 μm. The micrometre is a common unit of measurement for wavelengths of infrared radiation as well as sizes of biological cells and bacteria, and for grading wool by the diameter of the fibres.

The next smallest common SI unit is the nanometre, equivalent to one one-thousandth of a micrometre, or one billionth of a metre ( 0.000 000 001 m). 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 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 0.000039 inch). A 6 μm diameter carbon filament above a 50 μm diameter human hair

Micrometer to meter