The square foot (plural square feet; abbreviated sq. ft, sf, ft2) is an imperial unit and U.S. customary unit (non-SI, non-metric) of area, used mainly in the United States and partially in Bangladesh, Canada, Ghana, Hong Kong, India, Malaysia, Nepal, Pakistan, Singapore and the United Kingdom. It is defined as the area of a square with sides of 1 foot.
Although the pluralisation is regular in the noun form, when used as an adjective, the singular is preferred. So, a flat measuring 700 square feet could be described as a 700 square-foot flat. This corresponds to common linguistic usage of foot.
1 square foot is equivalent to:
1 acre is equivalent to 43,560 square feet.