How to use the square footage calculator
- Choose a Shape: rectangle or square, circle, triangle, or I know the area.
- Enter the Length and Width, the Diameter, or the triangle’s Base and Height.
- Set the Number of identical areas if you have several of the same size.
- Optionally enter a Price per square foot to estimate the total cost.
How it works
The calculator finds the area of one shape and multiplies it by the number of identical areas. Results are shown in square feet, square meters, square yards and acres.
If you enter a price per square foot, the total is simply area × price. Material and labor quotes are often given this way.
Rectangle = length × width
Circle = π × (diameter ÷ 2)²
Triangle = ½ × base × height
Square yards = square feet ÷ 9; acres = square feet ÷ 43,560
Worked example
With the default inputs, a 12 × 10 ft room is 120 ft². That equals 11.15 m², 13.33 square yards and 0.0028 acres.
Two identical 12 × 10 ft rooms would total 240 ft², or 26.67 square yards.
Tips before you buy
- For L-shaped rooms, split the floor into rectangles, calculate each one and add them together.
- Measure wall to wall at floor level and round up to the nearest inch.
- Carpet is often priced per square yard; divide square feet by 9 to compare.
- Order flooring and other materials with a waste allowance on top of the bare area.
Frequently asked questions
How do I calculate square footage?
For a rectangle, multiply length by width in feet. A 12 × 10 ft room is 120 ft².
How do I convert square feet to square yards?
Divide by 9, since a square yard is 3 ft × 3 ft. 120 ft² is 13.33 square yards.
How many square feet are in an acre?
An acre is 43,560 ft².
How do I find the square footage of a circle?
Multiply π by the radius squared. A circle 10 ft across has a radius of 5 ft, so its area is about 78.5 ft².
How do I measure an irregular room?
Divide it into rectangles and triangles, work out each area separately, then add them. You can enter the total with the I know the area option in other calculators.
Results are estimates based on the measurements you enter and typical material properties. Products vary, so check quantities with your supplier and follow product labels and your local building codes. Read the full disclaimer. Last reviewed October 9, 2026.