A nanometre (American spelling: nanometer, symbol: nm) is 1.0×10⁻⁹ metres — or one billionth of a metre. It is an SI measure of length, commonly used in measuring the wavelengths of visible light (400 nm to 700 nm), ultraviolet radiation and gamma rays; amongst other things.

• 1 nm = 1000 picometre.
• 1000 nm = 1 micrometre ( or 1 micron)

In older (e.g. 1958) texts, the nm is sometimes denoted "mµ" for "millimicron", based on the old term "micron" for a micrometre. Double prefixes are not allowed in SI, and this is never seen in modern writing or speech.

picometre << nanometre << micrometre

See also

• 1 E-9 m
• SI
• SI prefix
• Orders of magnitude