Convert meters to millimeters (m to mm)

One meter is exactly 1,000 millimeters, by the meaning of the prefix.

Worked through: 1 m x 1,000 = 1,000 mm.

Going the other way, one millimeter is 0.001 meters.

For mental arithmetic: Move the decimal point three places right. 2.4 m is 2,400 mm.

Construction in metric countries works in millimeters and nothing else: a plan gives a wall as 2400, with no unit, and a 2.4 m figure is a conversion the reader is expected to do in their head. The danger is the separator. In much of continental Europe a full stop is a thousands separator, so '2.400' on a German drawing is two thousand four hundred millimeters, and in the US it would read as two point four. A number with three digits after a separator, on a drawing from another country, should be checked against the scale before anything is cut.

Precision is worth matching to the input. A measurement given as 0.1 m carries one or two significant figures, and reporting its conversion to six implies a precision the original never had.