ClutchCalcs

Construction

Square Footage Calculator

The most-asked question on every construction, flooring, painting, and real estate project: how many square feet? Square footage drives material orders (flooring, paint, drywall, siding, roofing), pricing (real estate price per sq ft, contractor quotes per sq ft), and code compliance (occupancy load, ventilation requirements). This calculator handles rectangles (most rooms), circles (round patios, pool surfaces), and triangles (gable end walls, attic floor areas). For L-shaped or irregular rooms, break into rectangles and add. Returns the area in square feet plus conversions to square meters and square yards.

Common applications

  • Flooring orders: sq ft ÷ (sq ft per box) = boxes needed. Add 10-15% waste for typical rectangular rooms, 20%+ for diagonal layouts or complex shapes.
  • Paint coverage: 1 gallon covers ~350-400 sq ft per coat. 2-coat job on average wall area = 175-200 sq ft per gallon.
  • Real estate: most US listings quote total square footage including all heated/cooled living space. Garage, attic, and unfinished basement are usually separate.
  • Tile: order 10% over actual area to account for cuts at edges; 15% for diagonal patterns.
  • Carpet: 10% waste minimum (more for patterned carpet); divide sq ft by 9 to convert to sq yards (carpet's standard unit).
  • Drywall: 4x8 sheets = 32 sq ft each. Wall sq ft ÷ 32 = sheet count. Add 10% for waste.

Shape formulas

  • Rectangle: length × width
  • Square: side²
  • Circle: π × (diameter / 2)² = πr²
  • Triangle (right): (base × height) / 2
  • Triangle (any): Heron's formula or (1/2) × a × b × sin(C)
  • L-shape: split into 2 rectangles; add areas
  • Trapezoid: ((top + bottom) / 2) × height

How to use this calculator

  1. Pick shape: rectangle, circle, or triangle.
  2. Enter dimensions in feet.
  3. Output: area in sq ft, sq meters, sq yards.
  4. For multi-room totals: calculate each room separately, sum the results.
  5. For irregular shapes: break into rectangles and triangles; add the results.

Common scenarios

Standard 12x14 bedroom for flooring. 168 sq ft. Plus 10% waste = 185 sq ft to order. At 22 sq ft per box of hardwood: 9 boxes.

Round patio 12 ft diameter. Area = π × 36 = 113 sq ft. For pavers at $5/sq ft installed: $565 for the patio.

Triangular gable end wall, 30-ft base × 6-ft peak height. (30 × 6) / 2 = 90 sq ft. For siding orders, add to total wall sq ft.

FAQ

How do I measure an L-shaped room? +
Break it into two rectangles. Measure the long arm of the L, then the short arm. Sum the areas. For an exact result, measure each leg from the inside corner outward.
Do I include closets in room square footage? +
For real estate: typically yes — closets count as living space. For flooring orders: depends on whether you're flooring inside the closet (usually yes for new builds, often no for replacement).
What about wall square footage for paint? +
Sum: (wall length) × (ceiling height) for each wall. Subtract large openings (windows over 25 sq ft, doors). Most paint calculators assume 8-ft ceilings and 350 sq ft coverage per gallon for one coat.
What's the difference between living area and total area on real estate listings? +
Living area ("finished" / "heated" / "livable"): the interior conditioned space — bedrooms, living rooms, kitchens, finished basements. Excluded: garages, unfinished attics, unfinished basements, open porches. Total area sometimes includes unfinished space and outdoor structures. ANSI Z765 is the closest US standard.
How do I measure square footage from a drawing? +
For floor plans drawn to scale: use the scale ruler indicator. Measure each room's dimensions on the drawing, multiply by the scale factor to get real dimensions. For digital plans: many CAD software tools have a built-in area measurement function.
How accurate does the measurement need to be? +
For ordering materials: within ±5%. For real estate listings: within ±2% (per ANSI standard). For permit / code applications: as drawn on permit documents.
Sq ft, sq yd, sq meter — when to use each? +
Sq ft: US convention for most residential applications. Sq yd: carpet, fabric, some landscape materials. Sq m: metric world (everything except US), some scientific applications. 1 sq yd = 9 sq ft. 1 sq m ≈ 10.76 sq ft.
How big is a typical room? +
Bedroom: 100-200 sq ft (small) to 250-400 sq ft (master). Living room: 250-500 sq ft. Kitchen: 100-250 sq ft. Bathroom: 30-100 sq ft (full bath); 30-50 (half bath). Garage (2-car): 400-600 sq ft.