A centimetre is equal to 10 millimetres, or the width of a fingernail. Inches provide another way to visualise the magnitude of a centimetre. An inch is approximately three times larger than a centimetre.
The metric system is used to measure a centimetre, as opposed to the imperial or American system. Commonly used to measure distances, a ruler features calibrated lines designated in either centimetres or inches, making it simple to compare the two systems. It may also be useful to compare the size of a centimetre to popular objects. Using orders of magnitude, or the scale of relationships between numbers, is a more exact method.