Square Footage Calculator
Calculate the area of a room or space in square feet (and square metres) for rectangles, squares, circles, triangles, and trapezoids — with optional cost and multi-room totals.
FreeNo sign-upPrivate — runs in your browser, nothing is uploaded
= 11.15 m²
Computed in your browser. 1 ft² = 0.0929 m².
Quick answer
Square footage is the area of a space measured in square feet. For a rectangular room, multiply length by width: a 12 ft × 10 ft room is 120 ft². This calculator handles rectangles, squares, circles, triangles, and trapezoids in feet, metres, inches, or yards, converts the result to both ft² and m², multiplies across several rooms, and can estimate material or flooring cost from a price per square foot.
Formula & method
Each shape uses its standard area formula: rectangle = length × width, square = side², circle = π × radius², triangle = ½ × base × height, and trapezoid = ½ × (base a + base b) × height. Lengths are converted to metres, the area is computed, and the result is shown in both square feet and square metres (1 ft² = 0.09290304 m²). Multiplying by quantity covers identical rooms, and the optional price per ft² gives a cost estimate.
Examples
- Input
- 12 ft × 10 ft
- Result
- 120 ft²
- Why
- Area = length × width = 12 × 10 = 120 square feet (≈ 11.15 m²).
- Input
- Circle, diameter 10 ft
- Result
- 78.54 ft²
- Why
- Radius = 5 ft, area = π × 5² = 78.54 ft².
- Input
- 12 ft × 15 ft
- Result
- 180 ft²
- Why
- 12 × 15 = 180 ft² — handy for estimating flooring or paint.
When to use this tool
- Estimating flooring, carpet, tile, or turf for a room or yard.
- Working out paint or material quantities from an area.
- Listing or comparing property and room sizes in ft² or m².
Common mistakes
- Mixing units in one calculation — measure every side in the same unit (all feet or all metres), not a mix.
- Using the diameter as the radius for a circle; the radius is half the diameter.
- Forgetting to add a waste allowance (usually 5–10%) when buying flooring or tile cut to fit.
Frequently asked questions
How do I calculate square footage?
For a rectangle, multiply length by width in feet. For other shapes, the tool applies the right formula automatically — just pick the shape and enter the dimensions.
Can I measure in metres or inches?
Yes. Choose feet, metres, inches, yards, or centimetres; the calculator converts and always shows the area in both square feet and square metres.
How do I handle an L-shaped room?
Split it into rectangles, calculate each one, and add them — or use the quantity field if the sections are identical.
How much extra material should I buy?
A common rule is to add 5–10% for waste, offcuts, and pattern matching. Add more for diagonal layouts or intricate rooms.
Does it estimate cost?
Yes. Enter a price per square foot and it multiplies by the total area (across all rooms) to estimate the cost.
Is anything uploaded?
No — the area and cost are computed in your browser.
Sources & references
External references open in a new tab. We are independent and not affiliated with these organizations.
- ✓ Free to use
- ✓ No sign-up required
- ✓ Runs entirely in your browser — nothing is uploaded.
- ✓ Formula and method shown above
Provided “as is” for general information only — results may be inaccurate, so verify before you rely on them. No warranty; use at your own risk.
Built and reviewed by HIFreeTools against the formula shown above and any authoritative references cited on this page. See our methodology and editorial standards.
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