Square Footage Calculator
Pick a shape, choose your units and enter the measurements. We give you the area in square feet, square metres and more.
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The formula
Rectangle: length x width. Circle: π x r². Triangle: base x height / 2. Trapezoid: (a + b) / 2 x height.
Measuring a room
For a simple room, multiply length by width. A 12 ft by 15 ft room is 180 square feet. For an L-shaped room, split it into two rectangles, find each area and add them together.
Other shapes
- Circle: half the width is the radius. A 10 ft round rug has a radius of 5 ft, so its area is 3.1416 x 25 = 78.5 sq ft.
- Triangle: base times height, then halve it.
- Trapezoid: add the two parallel sides, halve that, and multiply by the height.
Where square footage is used
Flooring, paint, carpet, rent and property listings, heating and cooling, and garden plans. For flooring or paint, add 5 to 10 percent for waste, or use the specific calculators on this site.
Examples to check
Type these into the calculator above to see how it behaves. Every result below was produced by the same calculator code that runs on this page.
| What you enter | What you get |
|---|---|
| Rectangle or square; Feet; Length: 12; Width: 15 | Area in square feet: 180 ft² |
| Circle; Feet; Radius: 5 | Area in square feet: 78.54 ft² |
| Triangle; Metres; Base: 6; Height: 4 | Area in square feet: 129.167 ft² |
| Trapezoid; Feet; Parallel side a: 10; Parallel side b: 14; Height: 8 | Area in square feet: 96 ft² |
Square Footage Calculator: frequently asked questions
How do I convert square feet to square metres?
Multiply by 0.0929. 100 sq ft is 9.29 m². The tool shows both.
Is square footage the same as floor area on a listing?
Not always. Property listings may measure internal walls, wall thickness or include non-living areas, so the numbers can differ.
How accurate is this estimate?
It is as accurate as the numbers you give it. Real-world amounts such as paint, concrete or fuel vary, so allow a margin.
Is what I enter in this tool saved or sent anywhere?
No. The calculation runs in your browser, so what you enter is not sent to our servers. We only count, anonymously, whether a tool ran successfully.
Is this tool free to use?
Yes. It is free, needs no sign-up and has no usage limit.
Last reviewed: October 3, 2026