Micrometres
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Micrometres".

A micrometre (American spelling: micrometer; symbol µm) is one millionth of a metre, or equivalently one thousandth of a millimetre. It is also commonly known as a micron. It can be written in scientific notation as 1×10⁻⁶ m, meaning 1/1 000 000 m.

The symbol µm's character µ (Unicode character U+00B5; HTML µ) is "micro-", which should look identical to the Greek letter mu (μ) (the two may or may not look the same, depending on the font). The symbol µm is sometimes replaced by "um" when a suitable glyph for µ is not readily available, for example in ASCII or when using a typewriter, although this is non-standard.

The micrometer is a common unit of measurement for wavelengths of infrared radiation. Some people (especially in astronomy and the semiconductor industry) use the old name micron and/or the solitary symbol µ (both of which were official^{citation needed} between 1879 and 1967) to denote a micrometer. This practice persists in the face of official discouragement, perhaps to help disambiguate between the unit of measurement and the micrometer, a measuring device.

Input

The µ symbol can be entered the following ways:

• Alt+230 - Alt code from CP437 and other IBM codepages; on Windows and DOS.
• Alt+0181 - Alt code from ISO-8859-1 etc; on Windows.
• AltGr+m - on many non-US keyboard layouts, also Option+m on a Mac.
• Ctrl+Shift+B5 - Unicode hex code; on Linux.

See also

• 1 E-6 m (for a comparative description of the micrometre in the context of other orders of magnitude)
• SI
• SI prefix
• Metric system
• Orders of magnitude
• Micronization