Square Feet Calculator: Area of a Room or Shape

Measure the surface you want to cover, calculate its area, then add an allowance for waste, because cuts, pattern matching and mistakes mean you need more than the net area. The product label or installation guide states its coverage and the extra to allow. For flooring use the floor area; for paint, add up the wall areas and subtract doors and windows.

A 10x10 room is 10 ft × 10 ft = 100 square feet, so the answer to "how big is 10x10 in sq ft" is 100. A 20x30 room is 20 × 30 = 600 sq ft. For any rectangle, multiply the two sides in feet.

Multiply length by width with both in meters, or choose meters in the unit menu and read the square meters result. To convert from square feet, multiply by 0.09290304: 120 square feet × 0.09290304 = 11.15 square meters.

One square foot is a square that measures 1 foot on each side, which is 12 inches × 12 inches = 144 square inches, or 0.09290304 square meters. An area in square feet counts how many of those squares fit in: a 3 ft by 4 ft rug covers 12 of them.

Multiply the wall’s width by its height in feet. Add up the walls you will paint, then subtract doors, windows and other openings: a 12 ft by 8 ft wall is 96 sq ft, and a 3 ft by 7 ft door takes 21 sq ft off, leaving 75 sq ft. Run the calculator once for each wall or opening and add or subtract the results.

A square yard is 3 ft × 3 ft = 9 square feet. An acre is 43,560 square feet, the area of a strip 660 ft long and 66 ft wide. The results list shows your area in square yards and acres too.

Measure each room, calculate its area and add them up, or measure the outside of the finished living space. Appraisals of single-family homes with an interior and exterior inspection must follow the ANSI Z765 method on loans sold to Fannie Mae (since April 2022) and Freddie Mac (since November 2023). It counts finished space above ground, measured at the exterior walls, and in general leaves out garages and unfinished areas. A listing or county tax record may count differently, so ask which convention applies.

Square footage is the area of a surface measured in square feet. For a rectangle, multiply the length by the width in feet: a 15 ft by 12 ft room is 15 × 12 = 180 sq ft. For other shapes use the shape menu: an L-shape is two rectangles added, a triangle is base × height / 2 and a circle is π × radius².

Measure wall to wall along the longest and the widest points with a tape measure, ideally at floor level, and write the numbers down. Enter decimals, such as 12.5 for 12 ft 6 in, or pick inches as the unit. Measure twice, and measure each section on its own if the room is not a simple rectangle.

Split it into rectangles, find each area and add them. Choose the L-shape option and enter the main rectangle and the second section: a 14 ft by 12 ft room (168 sq ft) with a 6 ft by 5 ft alcove (30 sq ft) is 198 sq ft. For an irregular room, divide it into rectangles and triangles, add the pieces and subtract any notch cut out of the room.

Calculate each room and add the results. The L-shape option adds two rectangles at once, so it also works for two rooms. For more rooms, note each total and add them: a 180 sq ft bedroom, a 120 sq ft kitchen and a 96 sq ft bath make 396 sq ft.

This calculator has no border mode, but the math is simple: find the area of the outer rectangle, find the area of the inner rectangle and subtract. A path 3 ft wide around a 20 ft by 10 ft garden makes an outer rectangle of 26 ft by 16 ft = 416 sq ft, so the path is 416 - 200 = 216 sq ft.

Choose a shape, pick the unit you measured in and enter the measurements. The square feet result updates as you type, with square yards, square meters and acres below it. Enter a price per square foot to see a cost estimate. It works as a square feet calculator for any room, wall or lot.

Divide the floor area by the area of one tile, both in the same unit, and round up, then add a spare allowance for cuts and breakage. A 120 sq ft floor with 12 inch tiles (1 sq ft each) needs 120 tiles, and with 6 inch by 6 inch tiles (0.25 sq ft each) it needs 480 tiles, before any allowance.

You cannot convert directly, because feet measure length and square feet measure area. You need a second length, and then you multiply the two. A board 10 ft long and 6 inches (0.5 ft) wide covers 10 × 0.5 = 5 square feet. For a room, multiply its length by its width.

An area has no single length, so you need one side to find the other. If the area is a square, the side is the square root of the area: 100 sq ft is 10 ft by 10 ft. For a rectangle, divide the area by the known side: 150 sq ft with a width of 10 ft has a length of 15 ft.