How to calculate square footage
Square footage is the area of a flat surface measured in square feet. For a rectangle, multiply the length by the width.
| Shape | Formula |
|---|---|
| Rectangle or square | length × width |
| Circle | 3.1416 × (diameter ÷ 2)² |
| Triangle | base × height ÷ 2 |
Worked example
A 12 × 10 ft bedroom is 120 sq ft. That is 13.33 square yards, or 11.15 m². A round patio 10 ft across is 3.1416 × 5² = 78.5 sq ft.
Measuring with feet and inches
Convert inches to decimal feet before you multiply: divide the inches by 12. A wall 10 ft 6 in long is 10.5 ft, and 11 ft 3 in is 11.25 ft.
| Inches | 3 | 4 | 6 | 8 | 9 |
|---|---|---|---|---|---|
| Feet | 0.25 | 0.33 | 0.5 | 0.67 | 0.75 |
Odd-shaped rooms
Break the space into rectangles, triangles and circles, measure each one, and add them together. For an L-shaped room, measure the two rectangles that make up the L. To remove an area, such as a kitchen island from a flooring order, calculate it separately and subtract it.
Common uses for square footage
| Project | What to measure | Tip |
|---|---|---|
| Flooring, carpet, tile | Floor area of each room and closet | Add 5 to 15 percent for waste depending on layout |
| Paint | Wall area: perimeter × height | Use the paint calculator to subtract doors and windows |
| Sod, seed, mulch | Yard or bed area | Split curved beds into simple shapes |
| Roofing | House footprint plus overhang | Multiply by the pitch factor; see the roofing calculator |
Always measure twice and write each measurement down with its unit. Most expensive ordering mistakes come from mixing feet with inches, or from forgetting a closet or hallway.
Unit conversions
| From | To | Multiply by |
|---|---|---|
| Square feet | Square meters | 0.0929 |
| Square meters | Square feet | 10.764 |
| Square feet | Square yards | ÷ 9 |
| Acres | Square feet | 43,560 |
| Hectares | Square meters | 10,000 |
Frequently asked questions
How do I calculate square feet of a room?
Measure the length and width in feet and multiply them. A 15 × 12 ft room is 180 square feet.
How many square feet are in a square meter?
One square meter equals 10.764 square feet. One square foot is 0.0929 square meters.
Is square footage the same as square feet?
Yes. Square footage is simply an area expressed in square feet.
How do I measure a room with a closet?
Measure the main room and the closet as separate rectangles and add their areas.