Full name: millimetre
Plural form: millimetres
Symbol: mm
Alternate spelling: millimeters
Category type: length
Scale factor: 0.001
The SI base unit for length is the metre.
1 metre is equal to 1000 millimetres.
Valid units must be of the length type.
You can use this form to select from known units:
A millimetre (American spelling: millimeter, symbol mm) is one thousandth of a metre, which is the International System of Units (SI) base unit of length. The millimetre is part of a metric system. A corresponding unit of area is the square millimetre and a corresponding unit of volume is the cubic millimetre.