How to measure square footage
Square footage is the area of a flat surface in square feet. For a rectangular room, measure the length and the width in feet and multiply them. Measure wall to wall at floor level, and round to the nearest half foot. If your tape shows feet and inches, divide the inches by 12: 12 feet 6 inches is 12.5 feet.
For a room with an alcove, a bay window or an L shape, split the floor into rectangles, work out each one and add them together. The L-shape option above does this for two rectangles. For more complicated rooms, run the calculator once for each rectangle.
Formulas for each shape
Rectangle = length × width
L-shape = (length A × width A) + (length B × width B)
Circle = 3.1416 × (diameter ÷ 2)²
Triangle = base × height ÷ 2
In the example above, a 12 × 15 ft room is 180 square feet. That is the same as 20 square yards or 16.7 square meters.
When you split an L-shaped room, make sure the two rectangles do not overlap. Measure part A across the full length of the room, then measure part B only for the section that sticks out beyond it.
Converting square feet
| Unit | Equals | Used for |
|---|---|---|
| 1 square yard | 9 sq ft | Carpet and some landscaping fabric |
| 1 square meter | 10.764 sq ft | Metric product specs |
| 1 acre | 43,560 sq ft | Lots and large lawns |
Square footage of a house
The square footage listed for a house in the US usually means its finished living area, measured from the outside of the exterior walls. Garages, unfinished basements and porches are usually listed separately. If you are measuring for a project, such as flooring or paint, measure the inside of each room instead.
Frequently asked questions
How do I calculate square feet from inches?
Multiply the length by the width in inches and divide by 144, since a square foot is 12 × 12 inches. A 30 × 60 inch area is 1,800 square inches, or 12.5 square feet.
How many square feet is a 12 × 12 room?
144 square feet, which is 16 square yards.
How do I measure a room that is not square?
Divide it into rectangles and triangles, calculate each part and add them together. For a room with angled walls, measure as if it were a full rectangle; the small extra area works as a safety margin when you buy materials.
How many square feet are in an acre?
43,560 square feet. A square acre is about 208.7 feet on each side.
For material quantities, use the calculator for your project, such as the flooring or tile calculator, which add the right allowance for waste.