Last updated: March 2026
What Is a Square Footage Calculator?
A square footage calculator converts room dimensions into total area in square feet, the standard unit for measuring floor space, wall surfaces, and material quantities in the United States. Whether you're buying flooring, estimating paint, or comparing home sizes, square footage is the number you need.
This calculator handles six different shapes — rectangles, circles, triangles, trapezoids, L-shapes, and multi-room combinations — so you can measure any space accurately. Enter your dimensions in feet and inches, meters, or yards, and get instant results in all four area units plus material estimates for tile, paint, carpet, and laminate.
Unlike basic calculators, this tool includes a built-in material estimator with waste factor, tile counts for four common sizes, paint gallons, carpet roll lengths, and a cost calculator. Everything updates in real time as you type — no "Calculate" button needed.
How to Calculate Square Footage
Rectangle or Square: Measure the length and width with a tape measure, then multiply them together. A 12' x 10' room is 120 square feet. If your measurements include inches, convert to decimal feet first (e.g., 12' 6" = 12.5 feet) or use this calculator's separate feet/inches fields.
Circle: Measure the radius (half the diameter) and use the formula A = pi x r squared. A circular patio with a 6-foot radius has 113.1 square feet of area. This calculator does the math automatically.
Triangle: Measure the base and the perpendicular height. The area is half the base times the height. A triangular alcove with an 8-foot base and 6-foot height has 24 square feet.
L-Shaped Room: Measure the overall width and length as if the room were a complete rectangle, then measure the cutout. Subtract the cutout area from the total. Or use our L-Shape mode which does this automatically.
Key Features
Six Shape Modes. Rectangle, circle, triangle, trapezoid, L-shape, and multi-room. Each has a live SVG diagram that updates as you enter dimensions, so you can visually confirm your measurements match reality.
Flexible Units. Enter dimensions in feet and inches (with separate fields for each), meters, or yards. Results display in square feet, square meters, square yards, and square inches simultaneously.
Material Estimator. Get instant estimates for tile (6x6, 12x12, 18x18, 24x24), paint gallons (1 and 2 coats at 350 sq ft per gallon), carpet (12-foot roll), and laminate boxes (20 sq ft per box). Toggle a 10% waste factor on or off.
Multi-Room Support. Add up to 20 rooms, each with its own shape and dimensions. The calculator totals all rooms together and applies material estimates to the grand total — perfect for whole-house projects.
Export Options. Copy results to clipboard, download a CSV spreadsheet, or print a formatted summary. Great for sharing with contractors, lumber yards, or home improvement stores.
Frequently Asked Questions
How do I calculate square footage?
Multiply the length by the width in feet to get square footage. For a room that is 12 feet long and 10 feet wide, the area is 12 × 10 = 120 square feet. For non-rectangular shapes, use the appropriate formula: circles use π × r², triangles use ½ × base × height, and trapezoids use ½ × (top + bottom) × height.
How do I convert square feet to square meters?
Multiply square feet by 0.0929 to get square meters. For example, 100 sq ft × 0.0929 = 9.29 sq m. To convert square meters back to square feet, multiply by 10.764. This calculator converts automatically between sq ft, sq m, sq yd, and sq in.
How much waste factor should I include?
A 10% waste factor is standard for most flooring and material projects. This accounts for cutting waste, measurement errors, and having spare material for future repairs. For diagonal tile patterns, increase to 15%. For complex room shapes with many cuts, 15-20% is safer.
How do I measure an L-shaped room?
Measure the overall width and overall length of the L-shape as if it were a complete rectangle. Then measure the cutout section that's missing. The area equals the overall rectangle minus the cutout. Alternatively, break the L into two rectangles, calculate each, and add them together.
How many tiles do I need per square foot?
The number of tiles depends on tile size. A 12×12 inch tile covers 1 sq ft, so you need 1 tile per square foot (plus waste). A 6×6 tile covers 0.25 sq ft, so you need 4 per square foot. An 18×18 tile covers 2.25 sq ft, and a 24×24 tile covers 4 sq ft. Always add 10-15% extra for cuts and breakage.