Millimetres.
The best unit for measuring the length of an ant is millimeters or centimeters. The ants are too tiny and the smallest unit of measurement would be ideal for them.
The best unit for measuring the length of a pencil is inches.
A millimetre.
meters
centimetres
Length in inches.
unit for measuring length
a tape measure
the meter.
Metres.
a tape measure
Feet and inches.