1. Spell out the type of measurement as in 35 square meters, 46 square kilometers.

2. For amounts less than 1, use zero before the decimal point as in 0.03.

3. When the decimal is 1 or less, the type of measurement is singular as in one mile, one foot, one kilometer, 0.35 meter, 0.55 cubic foot, 0.75 kilometer.

 

Source
Dragoman Style Guide for Figures