Square Footage Calculator
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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)
Quick tricks
- 1 sq yard = 9 sq feet, not 3. Converting between flooring units. A 12 × 15 ft room is 180 sq ft, which is 20 sq yards (180 ÷ 9), not 60.
- Average bedroom is ~120-200 sq ft. Sanity-checking your measurement. If your bedroom comes out to 50 or 500 sq ft, double-check the dimensions.
- Add 10% extra for flooring waste, 5% for paint. Buying materials. Cut waste, leftover pieces, and pattern matching always cost more than the raw area suggests.
- 1 acre = 43,560 sq ft, roughly the size of an American football field minus the end zones. Visualizing land area. A 1/4-acre lot is ~10,890 sq ft — about a 100 × 110 ft rectangle.
Examples
12 ft × 10 ft bedroom
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.
20 ft × 25 ft living room
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.