Square Footage Calculator
Enter one row per area and press Calculate. Split an L-shaped or odd room into rectangles, circles and triangles, and the calculator adds them up. Enter a price per square foot to estimate the cost of flooring, sod, paint and so on.
Square Footage Calculator
Square footage formulas
| Shape | Formula | Example |
|---|---|---|
| Rectangle or square | length × width | 12 × 15 ft = 180 sq ft |
| Circle | 3.1416 × (diameter ÷ 2)² | 10 ft across = 78.5 sq ft |
| Triangle | base × height ÷ 2 | 8 ft base, 6 ft high = 24 sq ft |
For a triangle, the height is measured at a right angle to the base, not along a sloping side.
Measuring a room
- Measure wall to wall at floor level, along the longest straight lines.
- Round up to the nearest inch, and write lengths as feet plus a fraction (12 ft 6 in = 12.5 ft).
- Split L-shapes, closets and bay windows into separate rectangles.
- For flooring, include closets. For paint, measure walls instead: wall width × ceiling height, minus about 20 sq ft per door and 15 per window.
Area unit conversions
| From | To | Multiply by |
|---|---|---|
| Square feet | Square yards | 0.1111 (÷ 9) |
| Square feet | Square meters | 0.0929 |
| Square meters | Square feet | 10.764 |
| Square inches | Square feet | 0.00694 (÷ 144) |
| Square feet | Acres | ÷ 43,560 |
Frequently asked questions
How do I calculate square footage?
Multiply the length by the width, both in feet. A room 12 feet by 15 feet is 12 × 15 = 180 square feet. If you measured in inches, multiply and then divide by 144.
How do I find the square footage of an L-shaped room?
Split it into two rectangles that don't overlap, work out each area, and add them together. Use one row per rectangle in the calculator.
How do I convert square feet to square yards or square meters?
Divide square feet by 9 for square yards, or multiply by 0.0929 for square meters. 180 sq ft is 20 sq yd or about 16.7 m².
How much extra flooring should I buy?
Buy 5–10% extra for straight-lay flooring and 15% or more for diagonal or herringbone patterns, to cover cuts and mistakes. Use the percentage calculator to add it.
How many square feet are in an acre?
One acre is 43,560 square feet, about the area of a square 208.7 feet on each side.
See also
- Concrete Calculator: Cubic yards and bag counts for slabs, footings and columns.
- Proportion Calculator: Solve A/B = C/D for the missing number, with steps.
- Percentage Calculator: Percent of a number, percent change, and increase or decrease by a percent.
Last updated: November 4, 2026