Square Footage Calculator
Calculate the total square footage of one or more equal rectangles with exact metric conversions.
Content updated August 5, 2026
This models equal rectangles only. Subtract openings or excluded regions separately; irregular outlines, installation waste, and sloped-surface area are not inferred.
Find the rectangular area of a room, wall, floor, garden bed, or other measured surface. Enter length and width in one unit and multiply the same dimensions across any number of equal spaces.
The headline is always square feet for easy material planning, with square metres and square yards alongside it. The calculation also reports area per rectangle and combined edge length, while keeping those different measurement types clearly labeled.
The Square Footage formula
Total area (ft²) = length (ft) × width (ft) × number of equal rectanglesPerimeter per rectangle = 2 × (length + width) · 1 international ft = 0.3048 m exactly · 1 ft² = 0.09290304 m² exactly.
Worked example
Two equal rooms measuring 12 ft by 10 ft each have 12 × 10 × 2 = 240 ft² total, equivalent to 22.2967296 m² or 26.6667 yd² before display rounding.
Assumptions, rounding, and limitations
Assumptions
- Length and width describe a rectangle and use the selected common input unit.
- Every counted rectangle has identical dimensions and does not overlap another counted area.
- International-foot and metric relationships follow NIST conversion factors.
Rounding: The engine retains floating-point precision through unit conversion and multiplication. Displayed areas and edge lengths show up to four decimal places.
Limitations
- Does not directly model triangles, circles, curves, sloped surfaces, wall openings, overlapping areas, or differently sized rooms.
- Does not add installation waste, product coverage, cuts, seams, grout, pattern repeats, defects, or spare material.
- Combined perimeter simply sums each equal rectangle's four edges and does not remove shared walls.
Sources
- NIST Guide to the SI, Appendix B: Conversion Factors — National Institute of Standards and Technology
Square the length conversion, not the final label
Area is length multiplied by width, so converting an area requires squaring the length factor. NIST defines the international foot as exactly 0.3048 metre; consequently one square foot is exactly 0.09290304 square metre.
The calculator converts both dimensions to feet before multiplying. It then uses the same exact length relationships to express the result in square metres and square yards.
Split irregular spaces into honest rectangles
For an L-shaped surface, measure two non-overlapping rectangles and add their areas. For openings or excluded regions, calculate them separately and subtract them rather than pretending the outside bounding rectangle is all usable area.
The repeated-area count is intended only for equal rectangles. Differently sized rooms should be calculated separately, especially when measurements or material waste differ.
Frequently asked questions
▶How do I calculate square footage?
Measure length and width in the same unit, convert each to feet, then multiply them. A 12 ft by 10 ft rectangle is 120 ft².
▶How many square feet are in a square metre?
One square metre is approximately 10.7639104 square feet, based on the exact international-foot definition.
▶Can I calculate several equal rooms at once?
Yes. Enter a whole-number area count. The calculator multiplies both area and the displayed combined perimeter by that count.
▶Does the calculator include material waste?
No. It reports geometric rectangular area only. Product layout, cuts, pattern matching, defects, and spare material require a separate allowance.
▶Can it calculate an irregular floor plan?
Not in one entry. Divide the outline into non-overlapping rectangles, calculate each, and add them; subtract excluded rectangles separately.
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Open calculator →Disclaimer: Square Footage Calculator results are estimates for general information and education only, and are not financial, tax, legal or medical advice. Verify important decisions with a qualified professional.