Square Footage Calculator: Rooms & Multiple Shapes
Enter room sizes in feet and inches to get total square feet. Add L-shaped parts, triangles or circles, take away cut-outs, and see sq yd and cost.
Tool inputs stay in your browser · optional AI search sends your query
Good to know: Scope: the floor (or flat) area of a room, house, deck, patio or yard in square feet, from up to four parts you measure in feet and inches: rectangles (length × width), right or other triangles (base × height ÷ 2), circles (π × radius², the radius is half the width across), and rectangular cut-outs you want to take away, such as a closet, kitchen island or fireplace hearth. The shape formulas are from Clemson Cooperative Extension (HGIC 1220); splitting an odd room into rectangles and adding them up, and the 5 to 10% extra for flooring, follow Home Depot’s guide; square yards, square meters and acres use NIST Handbook 44 (1 sq yd = 9 sq ft, 1 acre = 43,560 sq ft, 1 sq ft = 0.09290304 m² exactly). The extra percentage and price are your choice. Not included: wall or roof area, slopes, curved walls other than full circles, official “living area” rules used by appraisers and listings (they may leave out garages, unfinished rooms and low ceilings), and local prices or tax. Everything stays in this browser tab; nothing is sent or saved. Independent ToolsKo estimate. Sources reviewed November 11, 2026.
How to use it (step by step)
- 1Measure the room wall to wall with a tape measure. You can type feet (12 or 12.5) or feet and inches (12' 6" or 12 ft 6 in).
- 2For an L-shaped or odd room, split the floor into simple pieces: put each rectangle, triangle or circle in its own area, and use “Cut-out” to take away a closet or island you are not covering.
- 3Read the total square feet, square yards and square meters. Add an extra percentage for flooring or tile (5 to 10% is common) and a price per square foot for a cost estimate.
Words to know
- Square foot (sq ft)
- The area of a square 1 foot on each side. A room 12 ft long and 10 ft wide is 12 × 10 = 120 square feet.
- Square yard (sq yd)
- A square 3 feet on each side, which is 9 square feet. Carpet is often sold by the square yard.
- Diameter and radius
- The diameter is the distance straight across a circle through the middle; the radius is half of that.
- Waste or overage
- Extra material you buy to cover cuts, breakage and mistakes, usually 5 to 10% for flooring and tile.
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Sources & methods
- Clemson Cooperative Extension HGIC 1220: Measuring the Area of a Home Lawn (rectangle, triangle and circle area formulas) ↗
- NIST Handbook 44 (2025), Appendix C: General Tables of Units of Measurement (1 sq yd = 9 sq ft, 1 acre = 43,560 sq ft, 1 sq ft = 0.09290304 m²) ↗
- The Home Depot: How to Calculate Square Footage (length × width, split odd rooms into rectangles, 5 to 10% extra) ↗
References checked November 11, 2026. Read each tool’s scope and assumptions before relying on its result.