Square Footage Calculator
Calculate the area of any room, lot, or whole floor. Add as many spaces as you need, mix units freely, and get the total in square feet, square yards, square meters, and acres.
Add more areas to total a whole floor or lot at once.
How to calculate square footage
Square footage is just area. Find the area of each space, then add them up. Always work in the same unit — convert inches to feet by dividing by 12 before you multiply.
Length × Width. A 12 ft × 10 ft room = 120 sq ft.
π × radius². Radius is half the diameter. A 10 ft circle = 3.14159 × 5² ≈ 78.5 sq ft.
½ × base × height. A 12 ft base × 8 ft height = 48 sq ft.
sq ft ÷ 9 = yd² · sq ft ÷ 10.764 = m² · sq ft ÷ 43,560 = acres.
Sources & assumptions
Frequently asked questions
How do I calculate square footage?
For a rectangular room, multiply length by width in feet: a 12 ft × 10 ft room is 120 square feet. For other shapes use circle = π × radius², triangle = ½ × base × height. To get a whole floor, calculate each room and add them together.
How do I find the square footage of multiple rooms?
Measure each room separately, calculate its area, then add the areas together. This calculator does that for you — click 'Add another area' for each room and it sums the total automatically.
How many square feet are in a square yard?
There are 9 square feet in 1 square yard (3 ft × 3 ft). To convert square feet to square yards, divide by 9. Flooring and carpet are often priced per square yard.
How many square feet are in an acre?
One acre is 43,560 square feet. To convert square feet to acres, divide by 43,560.
Should I add a waste percentage?
Yes, when you're buying flooring, tile, or sod. Cuts, broken pieces, and pattern matching mean you need extra — typically 5–10% for straight layouts and up to 15% for diagonal or patterned installs.