A micrometre or micron (American spelling: micrometer; symbol µm) is one millionth of a metre, or equivalently one thousandth of a millimetre or one thousand nanometres. It can also be written in scientific notation as 1×10⁻⁶ m, meaning m.

A strand of human hair is about 100 µm wide. Red blood cells are approx. 8 µm in diameter.
The micrometre is a common unit of measurement for wavelengths of infrared radiation. The name micron and the solitary symbol µ (both of which were official between 1879 and 1967 , "Abrogation of earlier decisions (micron, new candle)".) are still used (especially in astronomy and in the semiconductor industry) to denote a micrometre.

See also

• 1 micrometre (for a comparative description of the micrometre in the context of other orders of magnitude)

• SI

• Metric system

• Orders of magnitude