Square Footage Calculator
Rectangles, circles and triangles, added up.
Work out Square Footage. Rectangles, circles and triangles, added up. Coverage rates and densities are yours to set from the supplier's own figures.
For an L-shaped room, measure the other rectangle and add it here.
Square footage
120.0 sq ft
13.33 sq yd · 11.15 m²
Nine square feet to the square yard, since a yard is three feet and area scales with the square. For an L-shaped room, measure each rectangle separately and add them rather than looking for one formula.
How the Square Footage Calculator works
Square footage is length times width, and the only reason it goes wrong is that rooms are rarely one rectangle. Measuring each section separately and adding them is the reliable method, which is what this does — along with the conversion to square yards for flooring and square metres for anyone ordering in metric.
Also known as: square feet calculator · area calculator in feet · room square footage calculator · how to calculate square footage
The calculation itself
Length times width, both in feet. A circle is π times the radius squared, where the radius is half the diameter you measured. A triangle is half the base times the height.
Nine square feet make a square yard — a yard is three feet and area scales with the square, which is why the conversion is nine rather than three.
One square foot is 0.09290304 square metres, exactly, because a foot is exactly 0.3048 metres. That conversion has no rounding in it at all.
In practice
A 12 by 10 room is 120 square feet: 13.33 square yards, or 11.15 square metres.
Rooms are rarely one rectangle, and that is the only real difficulty. For an L-shape, split it into two rectangles, work each out and add them — more reliable than hunting for a formula that fits the whole outline.
The circle case is where orders go badly wrong. This asks for the diameter, straight across the widest point, because that is the measurement you can physically take. Enter a diameter into a calculator expecting a radius and the answer is four times too large, since area goes as the square.
Where the figure deceives
Square footage for a material order and square footage for a property listing are different exercises. Listings follow local conventions about what counts as finished space; a flooring order counts everything you are covering, closets included.
It also says nothing about how much to buy. Waste depends on the material and the pattern rather than the room — a diagonal floor or a repeating pattern wastes far more than a plain square lay, which is why waste is a separate input on the tools that need it.
And measuring at floor level can mislead on a room with sloped ceilings or deep skirting. For paint, the wall area is what matters, and that is a different measurement again.
Acting on it
Measure each rectangle separately and write the numbers down before multiplying anything. Most errors here are transcription rather than arithmetic.
Measure twice at both ends of a room. Walls are rarely parallel, and the difference matters when you are cutting flooring to a wall that is out of square.
Convert to the unit your supplier prices in before comparing quotes — square yards for carpet, square metres for most imported flooring.
Frequently asked questions
How do I calculate square footage?
Multiply length by width, both in feet. For an L-shaped room, split it into rectangles, work each one out and add them. That is more reliable than trying to find a single formula for an awkward shape.
How do I measure a circular area?
Measure straight across the widest point — that is the diameter — and the area is π times the radius squared, where the radius is half the diameter. Entering a diameter where a radius is expected makes the answer four times too large, which is why this asks for the measurement you can actually take.
How many square feet in a square yard?
Nine, since a yard is three feet and area scales with the square. Carpet and some flooring are priced by the square yard, so the conversion matters at the till.
Should I include closets and alcoves?
For flooring, yes — anything you are covering. For a property listing, the convention differs by market and by what counts as finished space, so a measurement for a sale is a different exercise from a measurement for a material order.
How much extra should I order?
It depends on the material and the pattern rather than the room. Flooring with a diagonal or a repeating pattern wastes far more than a plain square-laid tile, which is why waste is a separate input on the tools that need it.
Put this calculator on your own site
Free to use, on any site, commercial or not. Paste this where you want it to appear. It is a plain iframe, so it works in WordPress, Squarespace, Wix, Webflow, Ghost and anything else that accepts HTML.
<iframe src="https://www.thecalclibrary.com/embed/square-footage-calculator" width="100%" height="640" style="border:1px solid #e2e8f0;border-radius:12px" loading="lazy" title="Square Footage Calculator"></iframe>The only condition is that the credit line stays visible. It sits inside the frame, so you do not have to do anything to keep it.
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