A square nanometer.
Square metre
That one!
Metric ruler
Centimetre
You would use square metres (m2) to find the area of a door.
To find the area of a book cover in metric units, the most appropriate unit to use would be centimeters. The formula for finding the area of a book cover would be: length x width.
square meter
Square meters.
Square metres
meters2
A square nanometer.
Square metre
Square meters, generally.
Square centimetre.
cm for a reg. hb pencil it's about 1 cm
If it's a standard book, the standard units would probably be cm2.