Convert millimeters to meters (mm to m)

One millimeter is exactly 0.001 meters, by the prefix. Milli is a thousandth.

Worked through: 250 mm x 0.001 = 0.25 m.

Going the other way, one meter is 1,000 millimeters.

For mental arithmetic: Move the decimal point three places left. For square millimeters to square meters, six places.

One of the searches behind this pair is 'convert mm2 to m2', and that is a different conversion with a different factor. A millimeter is a thousandth of a meter, but a square millimeter is a millionth of a square meter and a cubic millimeter a billionth, because area squares the factor and volume cubes it. Electrical cable is sized by cross-section in square millimeters (1.5, 2.5, 6), and dividing 2.5 mm2 by a thousand gives 0.0025 m2, which is a thousand times too large. This conversion is for length only. For areas, divide by 1,000,000.

Precision is worth matching to the input. A measurement given as 1 mm carries one or two significant figures, and reporting its conversion to six implies a precision the original never had.