a cm
A metre.
always the meter to measure length. This is an SI (international) unit of measurment, and is the standard international unit of measurment for length.
Use a ruler.
cm
Inches
The ISO length unit to use would be the cementer.
You would use meters.
I would use feet
a ruler
You would use the SI unit meter (m) to measure the length of a DVD case.
miles or kilomiters
Kilometers are a unit of length, used to measure distance.