Square Footage Calculator

The short answer

Area is length times width: a 12 by 14 foot room is 168 square feet. For flooring and tile, measure the net area and add the waste factor. For painting, measure gross wall area — perimeter times height — and deduct doors and windows. Ceiling height does not change square footage but it changes volume, and the two answer different questions.

What it depends on

What counts as the room changes the answer. Alcoves, recesses and bay windows add area that a simple rectangle misses, and a room measured at the skirting includes wall thickness that the floor covering does not. Measuring at multiple points matters more on older buildings, where nothing is square, than on new ones. Whether to include a hallway or a closet depends on what the figure is for.

Where this stops being useful

This is arithmetic on the dimensions entered and inherits any measurement error. For material ordering, a professional measure is the authoritative figure, and for anything legal — a lease, a sale, a tax assessment — the measurement standard that applies is set locally. General information and planning only.

The most reliable way to avoid an inflated number is to break the space into rectangles and add them at the end, rather than multiplying the longest dimension by the widest. A room that is L-shaped is not one rectangle, and measuring it as one counts floor that does not exist. The same applies to anything that projects into the room: a chimney breast, a bank of fitted cupboards, a stair run, a boxed-in pipework. Measure the actual floor you intend to cover, and decide deliberately whether a chimney breast counts. For carpet and vinyl, it usually does not. For a whole-room paint calculation or an underfloor heating loop, it usually does.

This measurement turns up in almost every renovation conversation, often because two people disagree about it. A contractor quoting from the plan and a homeowner measuring with a tape will often not agree, and the difference is usually a chimney, a bay, or a section of floor the plan rounds off. Getting a figure both sides accept early avoids the kind of small disagreement that turns into a dispute about the whole job.

Once you have a square figure, the next step differs by material and the difference is large enough to matter. Carpet and vinyl are sold by the square yard in most markets, so divide by nine and round up before ordering. Tiles are sold by the box and the box rarely divides evenly into a room, which is why a tile calculator takes the box coverage as its main input rather than the area alone. Flooring sold by the length needs the board lengths you can actually get, which is a different calculation entirely. Do the area first, then hand it to the material-specific calculator rather than trying to do both in one step.

Square footage is the most quoted number in property and renovation, and the simplest to get wrong. The basic calculation is length times width, but real rooms are rarely perfect rectangles: alcoves, chimney breasts, bay windows, cupboards and under-stair areas all complicate the outline, and whether they count depends on what you are measuring for. For flooring or tiling, the answer you need is the usable area within the walls, and awkward shapes are best split into rectangles and added together. For estate-agent style measurement, conventions differ from country to country and sometimes ignore certain areas entirely, so a figure that is correct for ordering carpet may not match a listing. Knowing which number you are after prevents a costly misunderstanding. Units are the other source of confusion. A square metre is about ten and three-quarters square feet, so a room measured as twenty square metres is roughly two hundred and fifteen square feet, not sixty-five. When comparing quotes from suppliers who use different units, convert both to the same measure before comparing prices — a quote per square metre always looks cheaper than the same price per square foot. This calculator multiplies length by width, handles a number of identical rooms at once, and restates the result in square feet, square yards and square metres, with an optional cost. For an irregular room, measure it as several rectangles and run them separately, then add. Always measure at floor level rather than trusting a plan, since plans and reality often differ.

This calculator returns estimates for planning and general information only. It is not engineering, architectural, structural, electrical or code advice, and it cannot replace a qualified professional who has seen the site. Material quantities depend on the actual dimensions, the product you buy and local building codes, so confirm the figures before ordering materials or starting work, and always follow local regulations.