The square foot (pl. square feet; abbreviated sq ft, sf, or ft²; also denoted by '²) is an imperial unit and U.S. customary unit (non-SI, non-metric) of area, used mainly in the United States and partially in Canada, the United Kingdom, Bangladesh, India, Nepal, Pakistan, Ghana, Liberia, Malaysia, Myanmar, Singapore and Hong Kong.^{[citation needed]} It is defined as the area of a square with sides of 1 foot.

Although the pluralization is regular in the noun form, when used as an adjective, the singular is preferred. So, an apartment measuring 700 square feet could be described as a 700 square-foot apartment.^{[citation needed]} This corresponds to common linguistic usage of foot.

The square foot unit is commonly used in real estate.^[1] Dimensions are generally taken with a laser device, the latest in a long line of tools used to gauge the size of apartments^[2] or other spaces. Real estate agents often measure straight corner-to-corner, then deduct non-heated spaces, and add heated spaces whose footprints exceed the end-to-end measurement.^[3]

1 square foot conversion to other units of area:

• 1 square foot (ft²) = 0.000022956341 acres (ac)
• 1 square foot (ft²) = 0.000009290304 hectare (ha)
• 1 square foot (ft²) = 0.09290304 square meters (m²)
• 1 square foot (ft²) = 144 square inches (in²)
• 1 square foot (ft²) = 0.111111111111 square yards (yd²)
• 1 square foot (ft²) = 929.0304014422 square centimeters (cm²)
• 1 square foot (ft²) = 9.290304 square decimeters (dm²)
• 1 square foot (ft²) = 0.00000009290304 square kilometers (km²)
• 1 square foot (ft²) = 144,003,673,094,580 square microinches (μin²)
• 1 square foot (ft²) = 92,903,040,000 square micrometers (μm²)
• 1 square foot (ft²) = 0.0000000358701 square miles (mi²)
• 1 square foot (ft²) = 92,903.04 square millimeters (mm²)