How the square footage calculator works
- Rectangle: area = length × width
- Triangle: area = ½ × base × height
- Circle: area = π × (diameter ÷ 2)²
Feet and inches are converted to decimal feet first (inches ÷ 12). For example, 10 ft 6 in becomes 10.5 ft. Then the area is converted: square yards = sq ft ÷ 9, square meters = sq ft × 0.0929 and acres = sq ft ÷ 43,560.
L-shaped or irregular spaces: split the space into rectangles and triangles, calculate each one, and add them together.
Assumptions
- Measurements are taken at floor level, wall to wall.
- Results are rounded to two decimal places for display. Calculations use full precision.
Worked example
A room measures 12 ft 6 in × 10 ft.
- Convert: 12 ft 6 in = 12.5 ft
- Area: 12.5 × 10 = 125 sq ft
- That's 125 ÷ 9 = 13.89 sq yd, or 11.61 m²
Tips before you buy
- Measure each wall twice. Older houses are rarely perfectly square.
- Round measurements up to the next inch when buying materials, never down.
- Write measurements on a quick sketch of the room as you go.
Frequently asked questions
How do I calculate square footage?
Multiply the length by the width, both in feet. If a measurement includes inches, divide the inches by 12 and add them to the feet first.
How do I find the square footage of an L-shaped room?
Divide the room into two rectangles, calculate the area of each, and add them together.
How many square feet are in an acre?
One acre is 43,560 square feet.