**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 mm.

Valid units must be of the **length** type.

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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.

mm to football field [U.S.]

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