📏 Square Footage Calculator

What This Calculator Does

This calculator turns measurements into square footage. Enter a length and width in feet (decimals handle the inches) and it gives the area in square feet — plus square yards and square meters, since materials and listings mix all three. Add a price per square foot and it also totals the cost, which is how flooring, tile, paint, and most US home projects are actually quoted.

Square footage is the fundamental number of American home projects and real estate alike. Getting it right is the difference between buying the correct amount of material and either running short mid-job or overspending — and the calculation itself takes seconds once the measurements are in hand.

Measuring and Calculating Area

For a rectangle, area is length times width: a 12 × 10 room is 120 square feet. Measurements with inches convert by dividing the inches by 12 — 12 feet 6 inches is 12.5 feet — so 12' 6" × 10' 3" becomes 12.5 × 10.25 = 128.1 sq ft. For rooms that are not simple rectangles, the technique is decomposition: split an L-shape into two rectangles, calculate each, and add them. Any floor plan reduces to rectangles this way, measured one at a time.

Unit conversions matter because pricing is inconsistent. Carpet is traditionally sold by the square yard (nine square feet), so 270 sq ft of carpet is 30 square yards. International materials and specifications use square meters (one is about 10.76 sq ft). Seeing all three units at once — as this calculator shows — prevents the classic mistake of comparing a per-yard price against a per-foot price as if they were equivalent, an error that makes carpet look nine times more expensive than it is.

From Area to Project Costs

Cost per square foot is the lingua franca of US home projects. Flooring at $4.50/sq ft across 128 sq ft is $576; tile, paint coverage, decking, and countertops all quote the same way. Multiply area by unit price and you have the material budget — before the store visit, which is when you want it. The experienced-DIYer rule: buy about 10% extra for cuts, breakage, and pattern matching; running one box short of flooring mid-install, then discovering the dye lot changed, is the error the margin prevents.

Real estate speaks the same language at larger scale. Homes are listed and compared by square footage, and price per square foot is the standard yardstick for whether a listing is expensive for its market — a $360,000 house at 1,800 sq ft is $200/sq ft, directly comparable to the neighborhood's norm. Renovation quotes, rental spaces, and property taxes lean on the same figure. Whether the project is a bathroom floor or a house purchase, the workflow is identical: measure, multiply, and let the per-square-foot number do the comparing.

Measuring Rooms the Way Professionals Do

Accurate area starts with accurate measurement, and a few habits make the difference. Measure along the floor at the baseboard, where walls actually meet the surface you are covering, and take each dimension twice — once at each end of the wall — because rooms are rarely perfectly square; use the larger figure for material purposes. A steel tape or laser measure beats pacing it off. For alcoves, closets, and bay windows that will receive the same flooring, measure them as their own small rectangles and add them in. Doorway thresholds typically join the room whose flooring runs through them. Sketching the room and writing dimensions on the sketch as you go prevents the classic error of a forgotten wall.

Irregular shapes yield to decomposition and a little geometry. Any straight-walled room splits into rectangles; a triangular nook is half of length times width; a semicircular bay is half of πr². For walls rather than floors — paneling, wallpaper, tile — the same logic applies vertically: wall length times height, minus openings. Ceilings match the floor area in ordinary rooms. And when ordering, remember that materials sold in fixed units (boxes of flooring covering 22.5 sq ft, sheets, rolls) round your requirement up to whole units before the 10% waste margin — the calculator gives the true area, and the purchase quantity is that area translated into the units your material actually ships in. Measured this way, estimates land within a box or two of reality, which is exactly where you want them.

Quick Tips

• Area = length × width in feet; convert inches by dividing by 12 (6" = 0.5').
• Split L-shaped rooms into rectangles and add the areas.
• 1 square yard = 9 sq ft (carpet pricing); 1 square meter ≈ 10.76 sq ft.
• Buy ~10% extra material for cuts, waste, and pattern matching.

Frequently Asked Questions

How do I calculate square footage?

Multiply length by width, both in feet. A 12 x 10 room is 120 square feet. For L-shaped or complex spaces, split them into rectangles, calculate each, and add the areas together.

How do I handle measurements with inches?

Convert inches to a decimal of a foot first: divide inches by 12. So 12 feet 6 inches is 12.5 feet. The calculator accepts decimal feet, making 12' 6" x 10' 3" simply 12.5 x 10.25 = 128.1 sq ft.

How many square feet are in a square yard?

Nine — a yard is 3 feet, so a square yard is 3 x 3. Carpet is often priced per square yard: divide square feet by 9. And one square meter is about 10.76 square feet.

How is cost per square foot used?

Multiply the area by the unit price: 120 sq ft of flooring at $4.50/sq ft is $540 in material. It is the standard way flooring, tile, painting, and real estate are priced in the US — and always buy about 10% extra material for cuts and waste.

Practical, Instant, and Free

This calculator runs entirely in your browser, computing area and cost the moment you type. It needs no account or download and works on any device. Like every tool here, it is free to use as often as you like.

Related Tools

For more project math, the paint calculator estimates paint for walls, the length converter switches feet and meters, and the percentage calculator handles the 10% margin.