Centimetres.
By unit of length and distance and conversion ,we can say that the most appropriate unit to measure the length of a finger is cm.
Inches
cm
always the meter to measure length. This is an SI (international) unit of measurment, and is the standard international unit of measurment for length.
I would use feet
You would use meters.
yards
feet
miles or kilomiters
inch
miles
A metres, for an approximate measure, a centimetre for a more accurate measure.