Square Footage Calculator

Square footage is length × width for a rectangle, measured in feet. Measure at floor level rather than along the baseboard, and take each dimension twice at different points — few rooms are truly square, and a 3-inch difference across a 15 ft wall is nearly 4 sq ft of material.

That is 180 sq ft. Carpet is priced per square yard, so divide by 9 to get 20 square yards — the number that shows up at checkout and surprises people who budgeted per square foot. In metric it is 16.7 square meters, and with a 10% waste allowance you would order about 198 sq ft of flooring.

Split L-shaped and irregular spaces into rectangles, measure each, and add them up, including closets and alcoves that get the same flooring. For a triangle use half the base times the height; for a circle use 3.1416 × radius². Bay windows and curved walls are usually squared off to the widest point, since flooring is cut from rectangular stock anyway.

Ten percent is the default for straight-laid plank, tile, and sheet vinyl. Go to 15% for diagonal or herringbone layouts and for rooms with many corners, and add more for patterned carpet that has to be matched across seams. Long, narrow rooms waste more than square ones, because more planks need cutting at the ends.

Paint is sold by wall area, not floor area — perimeter × height. Concrete, mulch, and gravel are sold by volume, so depth matters as much as area. Heating and cooling sizing starts from floor area but adjusts heavily for ceiling height, insulation, and window area, which is why a BTU estimate from square footage alone runs wide.