How to work out square footage
Square footage is the area of a flat surface measured in square feet. Each section is worked out on its own and added up, and cut-out sections are subtracted.
Rectangle = length × width
Triangle = ½ × base × height
Circle = 3.1416 × (diameter ÷ 2)²
Worked example
A 15 by 12 foot living room is 15 × 12 = 180 sq ft. That is 20 square yards (180 ÷ 9) or 16.72 square meters. At $3 per square foot, materials cost $540.
Measuring tips
- Measure wall to wall at floor level, in feet and inches.
- Round each measurement up to the next inch rather than down.
- Split L-shaped and T-shaped rooms into rectangles that do not overlap.
- For a bay window, add the bay as its own rectangle or triangle.
- Subtract fixed items you will not cover, such as a kitchen island, with a cut-out section.
Unit conversions
| From | To | Multiply by |
|---|---|---|
| Square feet | Square yards | ÷ 9 |
| Square feet | Square meters | × 0.0929 |
| Square meters | Square feet | × 10.764 |
| Square feet | Acres | ÷ 43,560 |
Next step
Once you know the area, the flooring, tile and paint calculators turn it into boxes, tiles and gallons with waste included.
Common questions
How do I calculate square footage?
Multiply length by width in feet. A 12 by 15 foot room is 180 sq ft. For odd shapes, split the space into rectangles, triangles and circles, work out each one and add them up.
How do I calculate square footage of an L-shaped room?
Split it into two rectangles that do not overlap. Measure each, multiply length by width, and add the two areas. Use Add a section above to do this automatically.
How many square feet are in a square yard?
9 square feet make 1 square yard, because a yard is 3 feet and 3 × 3 = 9. Carpet is often priced per square yard.
How do I convert inches to feet for area?
Divide inches by 12 before multiplying. 10 feet 6 inches is 10.5 feet. This calculator has separate feet and inch boxes so you do not have to convert.
How many square feet in an acre?
One acre is 43,560 square feet.