The square foot (sq ft, ft2) is a derived unit of area in the international mass and length units.
The unit is mainly used in real estate in the United States. In the rest of the world the square meter is used instead.
Definition of the square foot
One square foot is equal to 1⁄9 square yard.
From the Weights and Measures Act of 1985: PART VI: Measurement of area
Value in terms of the SI
One square foot is equivalent to 929.0304 square centimeters.
One square foot is also equivalent to:
The White House has 55 000 square feet of floor space, 5% less than the total area of an American football field.
The International Mass and Length Units
The International Mass and Length Units are units based on the international yard and the international pound.
They were created in 1959 when Australia, Canada, New Zealand, South Africa, the United Kingdom and the United States of America agreed upon a common definition of the yard and the pound.