If 1cm equals 10mm, then 50mm has to be equal to 5cm. Every 1cm is equal to 10mm. If it was 10cm then it would be equal to 100mm. Does that explain it? :)

Inch and centimeter are both linear units of measurement. They are used to measure small distance. The conversion is done by multiplying the inch measurement by 2.54. The above unit in centimeters equals 2.1 cm (Approximately).