Type the dimensions as you read them off the tape (15′ 6″, 15.5, or 4.72 m) and this calculator gives the area in square feet, square yards, square metres, square inches and acres, with an optional cost per square foot. It handles rectangles, L-shaped rooms (two rectangles), circles, triangles and trapezoids, and multiplies by a count for several identical areas. Use it before the flooring, paint, tile and mulch calculators.
Square footage calculator
How it works
- Rectangle = length × width; L-shape = the two rectangles added
- Circle = π × diameter² ÷ 4
- Triangle = base × height ÷ 2; trapezoid = (side A + side B) ÷ 2 × the distance between them
- Conversions: 9 sq ft per sq yd, 0.09290304 m² per sq ft, 43,560 sq ft per acre
Worked example
A living room measuring 15 ft 6 in by 12 ft 3 in:
- Shape: Rectangle or square
- Length: 15′ 6"
- Width: 12′ 3"
- How many of these: 1
- Price per square foot (optional): $0
The calculator gives:
- Area: 189.88 sq ft
- Square yards: 21.097 sq yd
- Square metres: 17.64 m²
- Square inches: 27,342 sq in
- Acres: 0.0044 acres
- Shape: 15.5 × 12.25 ft
15.5 × 12.25 = 189.875 sq ft, which is 21.1 sq yd or 17.64 m². Add an 8 × 6 ft alcove as an L-shape and the room is 237.9 sq ft. A 12 ft round patio is 113.1 sq ft.
Notes and limits
- Measure to the walls at floor level and include closets and doorways for flooring; measure to the outside of the eaves for roofing.
- Split odd rooms into rectangles and triangles and add them up; the count field multiplies identical pieces.
- Feet and inches can be typed as 15′ 6″, 15 ft 6 in, or 15.5. Metres need the unit: 4.7 m.
- For a circle enter the diameter, not the radius.
Frequently asked questions
How do I calculate square footage of a room?
Measure the length and width in feet and multiply. For 15 ft 6 in by 12 ft 3 in, that is 15.5 × 12.25 = 189.9 sq ft.
How do you find the square footage of an L-shaped room?
Split it into two rectangles, find each area and add them. The L-shape option here does that from four measurements.
How many square feet in a square yard?
9. Carpet is often sold by the square yard: divide square feet by 9.
How many square feet is a 12 foot circle?
113.1 sq ft (π × 12² ÷ 4).
How do I convert square feet to square metres?
Multiply by 0.0929. 200 sq ft is 18.6 m².
Sources
Last reviewed: 26 September 2026. The calculation is covered by automated tests with known answers taken from the sources above. Found an error? Please let us know.