Square footage calculator

How square footage is worked out

Area is length times width, with both measured in the same unit. In feet the answer is square feet; in metres it is square metres. Inches are turned into feet first, so 12 ft 6 in is 12.5 ft. You can type it either way: 12.5 or 12' 6".

• Rectangle or square: length x width.
• Triangle: base x height / 2, where the height is measured square to the base.
• Circle: 3.1416 x (diameter / 2)².

Odd-shaped rooms

Split the floor into rectangles and triangles that do not overlap, measure each one, and add them up. An L-shaped room is two rectangles. A room with one slanted wall is a rectangle plus a triangle. To take out a part, such as a chimney breast, work it out separately and subtract it yourself.

Worked example

12 ft x 10 ft = 120 sq ft, and 14 ft x 12 ft = 168 sq ft. Together that is 288 sq ft. One square foot is 0.0929 square metres, so 288 sq ft is 26.76 m². One square yard is 9 square feet, so it is also 32 square yards.

Before you buy

This is floor area only. Flooring, tiles and carpet need extra for cuts and waste: the flooring calculator and tile calculator add it for you. For a home's official floor area, the rules on what counts (stairs, walls, low ceilings) differ by country and by purpose.