How do you calculate square footage?

For a rectangular room, multiply length by width in feet, so 12 by 15 gives 180 square feet. For irregular rooms, divide the space into rectangles, measure each separately, and add the results, subtracting any area you are not covering such as a kitchen island footprint. Triangles are half of base times height. Circles are pi times the radius squared. Measure at the widest points including alcoves and closets you intend to cover, and measure twice, since flooring is priced by the square foot and errors compound directly into cost.

Two adjustments turn the raw number into an order quantity. Add 10 percent for waste on straightforward layouts and 15 to 20 percent for diagonal installations, patterned material that must be aligned, or rooms with many angles and obstacles, because every cut generates offcuts you cannot use. Buying an extra box beyond that is cheap insurance, since dye lots and product lines change and a future repair from the same batch is otherwise impossible. Related measures that get confused with this: linear feet measures length alone and is how trim and countertop edging are sold, cubic feet adds height and is what you need for concrete, mulch, and appliance capacity, and a room's square footage in a real estate listing follows measurement standards that may include or exclude spaces like finished basements depending on local convention.