What your result means
Square footage is the floor area of a space. It is what you need to order flooring, paint for a floor, sod, or to compare home and room sizes. Material quantities usually need extra for cuts and waste, so add 5–15% to the area when you buy, depending on the material and the shape of the room.
How to use the Square Footage Calculator
- Choose the shape: rectangle, circle or triangle.
- Enter the length and width in feet (diameter for a circle; base and height for a triangle).
- If you have several identical areas, enter how many.
- Optionally enter a price per square foot to estimate cost.
Formula and worked example
rectangle = length × widthcircle = π × (diameter ÷ 2)²triangle = base × height ÷ 2sq yd = sq ft ÷ 9 sq m = sq ft ÷ 10.7639 acres = sq ft ÷ 43,560
Worked example: a 12 ft × 15 ft room is 12 × 15 = 180 sq ft, which is 20 sq yd or 16.72 m². For an L-shaped room, split it into rectangles, work out each one and add them together.
How to measure square footage
Measure each wall at floor level with a tape measure, to the nearest inch, and convert inches to feet by dividing by 12 (6 inches is 0.5 ft). For irregular rooms, sketch the floor plan, split it into rectangles and triangles, and add the areas. Subtract anything you won’t cover, such as a kitchen island, when you are buying flooring.
Typical room sizes
| Space | Dimensions | Square feet | Square meters |
|---|---|---|---|
| Small bedroom | 10 × 10 ft | 100 | 9.3 |
| Primary bedroom | 14 × 16 ft | 224 | 20.8 |
| Living room | 16 × 20 ft | 320 | 29.7 |
| Two-car garage | 20 × 20 ft | 400 | 37.2 |
| Patio | 12 × 15 ft | 180 | 16.7 |
Examples only; measure your own space.
Assumptions and limits
- Material quantities usually need 5–15% extra for cuts and waste; this calculator gives the exact area.
- 1 ft = 0.3048 m exactly, so 1 m² = 10.7639 sq ft.
Frequently asked questions
How do you calculate square feet?
Multiply the length by the width, both in feet. A room 11 feet by 14 feet is 154 square feet. If you measured in inches, divide each measurement by 12 first, or multiply the inches together and divide by 144.
How do you measure square footage of an irregular room?
Sketch the room, split it into rectangles (and triangles if there are angled walls), measure each part, work out each area and add them together. Subtract areas you won’t cover, such as a fixed kitchen island.
How do I convert square feet to square meters?
Divide square feet by 10.7639. For example, 180 square feet is 16.72 square meters. To go the other way, multiply square meters by 10.7639.
How many square feet are in an acre?
An acre is 43,560 square feet, which is about 4,047 square meters. The calculator shows acres alongside square feet for large areas such as lots and lawns.
How much extra flooring should I buy?
A common rule of thumb is 5–10% extra for simple rooms and 10–15% for diagonal layouts or rooms with many corners. Check the manufacturer’s guidance for your product.
How do you calculate the square footage of a circle?
Multiply π (about 3.1416) by the radius squared. A circular patio 10 feet across has a radius of 5 feet, so its area is 3.1416 × 25 ≈ 78.54 square feet.
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About this calculator
Written and maintained by Ahsan Khan. See how every number is calculated, and the test cases checked on every update, on the methodology page.
Sources
- Putting the Best "Foot" Forward: Ending the Era of the U.S. Survey Foot, National Institute of Standards and Technology (NIST) (accessed Oct 11, 2026)
- U.S. Survey Foot: Revised Unit Conversion Factors, National Institute of Standards and Technology (NIST) (accessed Oct 11, 2026)
- How to Measure a Floor for a Flooring Installation, BuildDirect (accessed Oct 11, 2026)
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