Some units used to measure area are square mile and square kilometre . Every unit of length has a corresponding unit of area , namely the area of a square with the given side length . Thus areas can be measure in square metres ( m2 ) , square centimetres ( cm2 ) , square millimetres ( mm2 ) , square kilometres ( km2 ) , square feet ( ft2 ) , square yards ( yd2 ) , square miles ( mi2 ) , and so forth .