1millimeter is equal to 0.1 Centimeter,
so 1800mm x 0.1cm = 180cm.
So, 1800mm is equal to 180cm.
BUT we seriously cannot see 1800millimeter in a ruler, that's because ruler has only 12inches, equal to 30.48 centimeters, very far from 180centimeters. BUT 1800mm can be found on longer measurement tools.