What Is a Square Foot?
A square foot is the area of a square that measures 1 foot (12 inches) on each side, which is 144 square inches. Because NIST fixes the foot at exactly 0.3048 meters, a square foot is exactly 0.09290304 square meters.
How big is a square foot?
A square foot is the size of one 12 by 12 inch floor tile, and a sheet of letter paper doesn't cover it.
Familiar things, measured in square feet:
4 by 8 feet
Picture tiles: a 10 by 12 foot bedroom takes 120 of them. Common rooms are in the square footage chart, and whole homes in the average square footage of a house.
Square foot vs foot
A foot measures length and a square foot measures area, so they can't be converted into each other. Doubling the sides of a square quadruples its area: a 2 by 2 foot square is 4 square feet, not 2.
Trim, lumber and fabric are sold by the linear foot instead. To turn a length into area you need a width; the square feet to linear feet converter does that.
Abbreviations: sq ft and ft²
NIST uses ft² as the symbol for square foot and notes that sq ft is an abbreviation for the same unit. Every form below means square feet.
Listings, receipts and everyday writing.
The symbol, read "feet squared." The raised 2 means foot times foot.
ft² typed where a superscript isn't available, as in spreadsheets and code.
Closed up in URLs and data fields.
Use "square foot" for the unit and as an adjective (price per square foot), and "square feet" for any count other than one (500 square feet).
The square footage formula
For a rectangle, square footage is length times width, both in feet.
Square feet = length (ft) × width (ft)
A 12 by 15 foot room is 12 × 15 = 180 square feet. Circles, triangles and L-shapes have their own formulas in how to calculate square footage, or let the room calculator or the square footage calculator do the math.
Measured in inches? Divide square inches by 144, not 12. A 30 by 48 inch rug is 1,440 square inches, or 10 square feet.
Square foot conversions
Every factor below comes from NIST's general tables of units; the usual mistake is using the length factor (12 inches, 3 feet) instead of its square.
NIST phased out the U.S. survey foot at the end of 2022, so acres are now counted in international feet. An acre measured in survey feet was about 0.17 square feet larger, too small to matter on a lot or a house. For any other unit pair, use the area converter.
Where square footage matters
Listings, material orders and room AC charts all start from square feet.
Listings compare homes by price per square foot, and only finished, above-grade living space counts; see what counts as square footage.
Since April 1, 2022, Fannie Mae requires appraisers to measure with the ANSI Z765 square footage standard on appraisals with an interior and exterior inspection.
Sold by coverage area. Work out how much with the flooring calculator or paint calculator, and price the job with the painting cost estimator.
Room air conditioners are sized by square feet; whole-house systems need a Manual J load calculation. The BTU calculator starts from square feet.
Frequently asked questions
How big is a square foot?
It's a square 12 inches on each side, the size of a standard 12-inch floor tile. Nine of them make a square yard.
How many square inches are in a square foot?
There are 144 square inches in a square foot, because 12 inches times 12 inches is 144. To convert square inches to square feet, divide by 144.
Is a square foot the same as a foot?
No. A foot is a length of 12 inches, while a square foot is the area inside a 12 by 12 inch square, which is why it's written ft² with a raised 2.
What is the abbreviation for square feet?
The usual abbreviation is sq ft (or sq. ft.), and the symbol is ft². You'll also see sqft and ft^2, which mean the same unit.
How much is a square foot in square meters?
One square foot is 0.0929 square meters, and one square meter is about 10.76 square feet. The square feet to square meters converter handles any size.