Attometre (American spelling: attometer, symbol: am) is an SI measure of length that is equal to 10⁻¹⁸, or 1 quintillionth (atto-) of a metre. An electron's radius is thought to be about 1 am.

• 1 am = 1 × 10⁻¹⁸ metre

zeptometre << attometre << femtometre

See also

• 1 E-18 m
• SI
• SI prefix
• Orders of magnitude