Square Footage Calculator

Calculate square footage for a floor, room, or wall

Select a rectangle, circle, triangle, or four-wall room. Enter every length in feet. In four-wall mode, add wall height and subtract the combined area of doors and windows when that deduction suits the project. The result reports measured square footage, perimeter when defined, an optional material overage, and an estimated material cost from the price you enter.

rectangle = length x width; circle = π x (diameter / 2)²; triangle = base x height / 2

Room floor example and ordering area

A 20 ft by 12 ft rectangular floor contains 240 square feet and has a 64 ft perimeter. With 10% overage, the material target is 240 x 1.10 = 264 square feet. At an entered material price of $3.50 per square foot, the estimated material cost is 264 x $3.50 = $924. This is an area-based estimate; it does not round up to full cartons.

Gross wall area versus net wall area

Gross wall area is room perimeter multiplied by wall height. Net wall area subtracts the combined square footage of openings. Whether to subtract small openings depends on the product, labor method, and estimator, so enter only the deductions appropriate to your project.

From slab area to concrete bags

Square footage alone does not determine concrete quantity: multiply area by the required thickness in feet, then divide by the selected mix's finished-volume yield. For an arithmetic example, 90 sq ft at 4 in is 30 cubic feet; a product yielding 0.60 cubic foot per bag needs 50 bags before allowance. See the 80 lb concrete bag coverage table and calculator to compare thicknesses. Bag weight alone does not establish yield, and the example thickness is not a structural specification.

Roof square footage versus floor area

A room's floor area or a building's horizontal footprint is not automatically its sloped roof surface area. For a known, uniform roof pitch, use the roof pitch calculator for roof square footage to apply the slope multiplier to a measured horizontal roof projection. For example, 1,200 sq ft of projection at 6:12 becomes about 1,341.64 sq ft of sloped surface, before material allowance.

Include applicable eaves in the projection, do not substitute the sum of multiple interior floors, and do not count both a whole roof projection and its component projections. Mixed pitches and complex roof sections need separate calculations and a checked takeoff. The result is geometry, not a shingle-bundle order, installed cost or structural assessment.

Measure feet and inches consistently

The calculator accepts decimal feet. Convert inches to a fraction of a foot before combining them with a measurement in feet: 12 ft 6 in = 12 + 6/12 = 12.5 ft. For example, a room 12 ft 6 in by 10 ft is 12.5 x 10 = 125 square feet. Do not enter 12.6 for 12 ft 6 in; the decimal portion of a foot is not inches.

The international foot is exactly 0.3048 meter, so one square foot is 0.09290304 square meter. NIST publishes the current foot conversion factors. This calculator is intended for ordinary project measurements, not legacy U.S. survey-foot mapping.

Measure irregular rooms without double counting

For an L-shaped or stepped floor that the shape menu does not model directly, split the outline into non-overlapping rectangles. Calculate each section separately and add the results. For example, a 12 ft by 10 ft main section plus a 4 ft by 3 ft alcove gives 120 + 12 = 132 square feet. If a cutout is easier to measure, calculate it separately and subtract it from the enclosing rectangle. Keep each piece on the same scale and do not count overlapping space twice.

Use overage and cost as planning estimates

Overage is applied to the measured area before cost is calculated: order area = measured area x (1 + overage percentage). Enter the product's price per square foot to estimate material cost. Waste depends on room shape, pattern, cuts, defects, and repair stock; the entered percentage is your assumption, not a universal recommendation. The estimate excludes carton rounding, tax, delivery, accessories, labor, surface preparation, and minimum charges. For flooring purchased by the box, use the flooring calculator to calculate full boxes and leftover coverage; for general shape formulas, use the area calculator.

For a measured walkthrough of L-shaped and other irregular rooms, including a worked square-footage example and ordering checks, read how to calculate square footage for an irregular room.

Estimating loose aggregate instead? The gravel calculator separates measured volume from supplier-density weight and optional material cost.

Buying mulch by volume? The mulch calculator estimates bulk yards and whole bags from entered area, added depth and the bag label, with separate material-price scenarios.

Frequently asked questions

How many square feet are in a square yard?

One square yard equals 9 square feet because a yard is 3 feet on each side.

Can this calculate an L-shaped room?

Yes, by dividing it into non-overlapping rectangles and adding their square footage. Calculate each section separately with the rectangle mode.

Should I subtract every door and window?

Not always. The appropriate deduction depends on the material, installation method, and estimator. Enter the opening area only when it should reduce the measured surface for your project.

Is this the same as official home living area?

No. Real-estate and appraisal standards define which spaces count and how they are measured. This tool calculates geometric project area only.