Square Footage Calculator
Calculate square footage for rectangles, squares, circles, triangles, trapezoids and L-shapes with quantity, waste and cost estimates.
- Six common floor and surface shapes
- Converts feet, inches, yards, meters and centimeters
- Adds quantity, waste allowance and price per square foot
Calculator workspace
Enter the known values, calculate, and review the supporting figures and formula instead of relying on a single unexplained number.
What this Square Footage Calculator does
Square footage is a basic planning measurement for flooring, paint coverage, roofing, landscaping, room layouts, rental space and material purchasing. Real projects often involve more than one rectangle, mixed measurement units, waste allowances and repeated areas. This calculator supports several common shapes, converts the entered dimensions to feet internally, and keeps the raw geometric area separate from the quantity and waste-adjusted material area.
The workspace is designed for quick checking as well as repeatable planning. Inputs remain editable, the supporting figures are shown with the headline result, and the calculation runs locally in the browser. That makes it easy to change one assumption at a time, compare scenarios and copy or save a result together with the values that explain it.
Formula and calculation method
Area depends on shape; final material area = geometric area × quantity × (1 + waste %).
Choose the shape that best matches the measured area. Rectangles use length × width; squares use side²; circles use πr² with dimension A treated as the diameter; triangles use base × perpendicular height ÷ 2; trapezoids use (parallel side A + parallel side B) × height ÷ 2; and an L-shape is modeled as an outer rectangle minus a rectangular cutout. The calculator then multiplies by quantity, applies the waste percentage, converts the final area to square meters and square yards, and optionally estimates material cost from a price per square foot.
How to use the calculator
- Choose the calculation mode, shape, unit or known-value combination when the page provides one.
- Enter values that belong to the same problem or measurement scenario and keep units consistent with the field labels.
- Select Calculate and review both the main answer and the supporting metrics shown with it.
- Change one assumption at a time when comparing scenarios; this makes the effect of each input easier to understand.
- Use Copy Result, Share Result or Save Result Image when you need a portable record of the calculation.
Worked example
For a 12 ft × 10 ft rectangular room, base area is 120 sq ft. With a 10% waste allowance, the material planning area becomes 132 sq ft. If material costs 3.50 per sq ft, the estimated material amount is 462 before taxes, labor, underlayment, trim or other project costs.
How to interpret the result
Use waste as a planning allowance rather than a universal rule. Flooring patterns, tile cuts, board lengths, defects and room geometry can change the appropriate percentage. For irregular areas, divide the project into simpler shapes, calculate them separately, and add the results. When estimating purchasable packages, round up based on the manufacturer’s coverage per box, roll, sheet or bundle rather than rounding the square-foot result alone.
A calculator result is only as useful as the values entered. For measurements, use appropriately precise source data; for costs, use prices that match the same currency and period; for technical work, compare the output with drawings, equipment data or other authoritative information. The supporting metrics on this page are included specifically to make cross-checking easier.
Important assumptions and limitations
This tool calculates planar area; it does not account for slopes, three-dimensional surfaces, openings, material thickness, package sizes, seam direction or local construction requirements. Circle mode treats dimension A as the diameter. L-shape mode assumes the cutout is entirely inside the outer rectangle and aligned with its sides.
This calculator is provided for planning, checking, education and general informational use. It makes the formula and assumptions visible, but it does not replace project specifications, professional engineering, financial or medical advice, contractual documents, equipment ratings or applicable standards.
Frequently asked questions
How do I calculate square feet from inches?
Choose Inches as the dimension unit and enter the measurements normally. The calculator converts dimensions to feet before calculating area.
How much waste should I add?
It depends on the material and layout. Simple rooms may need only a modest allowance, while diagonal patterns or irregular cuts can require more. Check supplier guidance.
Can I calculate an L-shaped room?
Yes. Enter the outer rectangle as A × B and the rectangular cutout as C × D.