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A square footage calculator measures the area of a rectangular space, a room, a yard, a deck, a piece of carpet, by multiplying its length and width. Enter the dimensions in feet and the calculator returns square feet, square yards, and square meters. Useful for flooring estimates, paint coverage, landscaping, and real-estate listings.
For non-rectangular spaces (L-shapes, alcoves, irregular yards), break the space into rectangles, calculate each one separately, and sum the results. Most floor plans decompose into 2-4 rectangles cleanly; the math takes longer than the measuring.
Key takeaway
Square footage is just length × width, but the unit conversion catches people. One square yard equals nine square feet, not three (because both dimensions get tripled). Same for square meters and any other 2D unit conversion: square the linear conversion factor, don't just apply it.
How it's calculated
The area of a rectangle is length × width. Both dimensions in feet
produces square feet directly. Conversions:
- Square feet → square yards: divide by 9 (because 1 yd = 3 ft, and area is squared)
- Square feet → square meters: multiply by 0.092903
- Square feet → acres: divide by 43,560
For circular areas, use π × radius² instead. For triangles,
½ × base × height. This calculator handles the rectangular case, which
covers ~90% of household measurement needs.
Source: Elementary geometry, area of a rectangle (length × width)
Examples
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12 ft × 10 ft bedroom
Square feet 120.0
A 12 × 10 ft bedroom measures 120 square feet, which is about 13.3 square yards or 11.1 square meters. For carpeting, you'd want to order roughly 130-135 sq ft to allow for cuts and waste.
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20 ft × 25 ft living room
Square feet 500.0
A 20 × 25 ft living room is 500 square feet, large by US suburban standards. For paint coverage at the typical 350 sq ft per gallon rate, two coats would need about 3 gallons of wall paint (calculated on the perimeter × ceiling height, not floor area, but the floor area is a useful sanity check).
Frequently asked questions
How do I measure square footage of an irregular space?
Break the space into rectangles. Most floor plans, even L-shapes, T-shapes, and alcoves, decompose into 2-4 rectangles cleanly. Measure each rectangle's length and width, calculate its area, then sum all the areas. For curved walls, approximate as a series of small rectangles or use the formula for the relevant shape (circle, ellipse, triangle).
How much extra material should I buy for flooring?
Most professionals recommend 10% extra for tile and hardwood, 15% for diagonal patterns or complex layouts, and 5-7% for vinyl or laminate. Carpet is sold by the square yard or in fixed-width rolls, so the practical waste depends on how the room dimensions match the roll width. Always order from the same dye lot, color-match differences between batches are visible even if the SKU is identical.
How is square footage calculated for a house listing?
Real-estate square footage typically refers to the interior heated and cooled living area, measured from the inside of exterior walls. Garages, unfinished basements, and porches are usually excluded, though listing standards vary by region. Above-grade and below-grade finished areas are sometimes listed separately. The discrepancy between an MLS listing and a tape measure is one of the most common post-purchase surprises.
Is there a difference between sq ft and ft²?
No, they're the same thing. "Sq ft" and "ft²" are interchangeable notations for square feet. Mathematicians and scientific contexts prefer ft²; real estate, construction, and everyday speech prefer sq ft. Same unit, same value, just different conventions.