Square Footage Calculator

1. Measure each area's length and width in feet and inches. The example is 12 ft × 15 ft.
2. Multiply length by width: 12 × 15 = 180 sq ft. Turn inches into a part of a foot first: 6 in is 0.5 ft, so 12 ft 6 in is 12.5 ft.
3. Split an odd shape into rectangles, triangles and circles, find each one and add them. A triangle is half of base × height; a circle is π × radius², with the radius half the diameter.
4. Take away any cut-out, such as a hole or a bed, then convert: 180 sq ft ÷ 9 = 20 sq yd. The square meters are 180 × 0.3048 × 0.3048 = 16.72 sq m.

Square feet are length times width, both in feet. Enter each side in feet and inches, and the page adds the inches to the feet before it multiplies. The example room is 180 sq ft, and the drawing shows it to scale beside the form.

A rectangle takes its length and width. An L-shaped room is two rectangles, each measured on its own and added together. A circle takes its diameter, and a triangle takes its base and its height, with the area half of base times height.

Add up to six areas. Tick the box on any area that comes out of the total, such as a hole for a pond or a bed inside a lawn, and it is subtracted. The total is always the areas added less the cut-outs.

A square yard is 3 ft × 3 ft, so it is 9 sq ft. Divide square feet by 9 for square yards, and multiply square yards by 9 for square feet. The example room is 180 sq ft, which is 20 sq yd.

For a house, add up the rooms: length times width for each one, then the total of the rooms. Or measure the outside of each floor, multiply its length by its width, and add the floors. The outside measure runs past the walls, so it is larger than the space inside.

The square footage on a listing or an appraisal follows the rules of the appraiser or the listing, which may count or leave out areas such as porches and garages differently from your own measure. This page gives the number you measure, and those rules are theirs.

Boards are sold by length, so a floor or a wall of boards is counted in linear feet: the area divided by the width of one board in feet. 180 sq ft of boards 6 in wide is 180 ÷ 0.5 = 360 linear feet, before cuts and gaps. The board sizes are on the board foot calculator and on the actual lumber sizes page.

For a lawn, the sod calculator turns this area into pallets and rolls of sod, and the topsoil calculator gives the soil for the layer under it.

For beds and paths, the mulch calculator and the gravel calculator take the same area and a depth. A patio of pavers uses the paver patio calculator, and a poured slab the concrete slab calculator.

Sand for a base goes to the sand calculator. Each of these starts from an area and a depth, and the cubic yard calculator turns that depth into the yards to order.