How to Measure Square Footage
Measure any room or surface in square feet — rectangles, circles, triangles, and odd shapes.
Square footage is the area of a surface measured in square feet. Whether you're buying flooring, ordering paint, or laying sod, getting the area right is the first step. Here's how to measure it for any shape — then drop your numbers into the calculator below to skip the math.
Step by step
- Measure length and width in feet Use a tape measure to find the length and width of the space. If you measure in inches, divide by 12 to convert to feet.
- Multiply for rectangles For a rectangular or square area, multiply length by width. A 12 ft by 10 ft room is 120 square feet.
- Break up odd shapes For an L-shaped or irregular room, split it into rectangles, measure each, and add the areas together.
- Use shape formulas where needed For a circle, use π × radius². For a triangle, use ½ × base × height.
- Add a little for waste When buying materials, add 5–15% so cuts and offcuts don't leave you short.
Square footage formulas by shape
| Shape | Formula | Example |
|---|---|---|
| Rectangle | length × width | 12 × 10 = 120 sq ft |
| Square | side × side | 10 × 10 = 100 sq ft |
| Triangle | ½ × base × height | ½ × 12 × 8 = 48 sq ft |
| Circle | π × radius² | π × 5² ≈ 78.5 sq ft |
Once you have the area, the same number drives most material estimates — flooring boxes, gallons of paint, square yards of carpet, and more. The calculators below take it from there.
Frequently asked questions
How do I measure an irregularly shaped room?
Divide it into rectangles and triangles, measure each piece, and add the areas together. For curved areas, approximate with a circle or half-circle.
What if I measured in inches?
Divide each measurement by 12 to convert to feet before multiplying, or multiply the inches and divide the result by 144.
Do I measure differently for flooring versus paint?
Yes — flooring uses the floor area (length × width), while paint uses wall area (perimeter × wall height, minus doors and windows).