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Square Footage Calculator

Square footage for rectangles, circles and triangles.

Your measurementsEvery assumption editable01

Ignored for a circle.

For repeating identical rooms or sections.

AreaCalculated live02

Result

280sq ft

280 square feet

Area of one20 × 14 ft
280 sq ft
Total area
280 sq ft
In square yards9 sq ft per sq yd
31.11 sq yd
In square metres
26.01 m²

For an irregular room, split it into rectangles, calculate each and add them. That is more reliable than trying to average an odd shape, and it is what a fitter does on site.

There are nine square feet in a square yard, not three. Squaring the linear conversion is the single commonest error in area arithmetic, and it produces an answer three times wrong.

This is floor area. Materials sold by area almost always need a waste allowance on top, which the individual material calculators apply.

Area for the three shapes that cover almost every real job, with square yards and square metres alongside. For an irregular room, split it into rectangles and add them — which is what a fitter does anyway.

Why use this tool?What it does differently03

Why use this tool?

Three shapes

Rectangle, circle and triangle. Between them they cover almost every practical case.

Repeat count

For identical rooms or repeating sections, without running it several times.

Yards and metres

Square yards for carpet, square metres for anything with metric documentation.

The nine, not three

There are nine square feet in a square yard. Squaring the linear conversion is the classic error.

How this worksThe method04

How this square footage calculator works

Rectangle is length times width. Circle is π times the radius squared, with the diameter entered as the length. Triangle is half the base times the height.

Square yards divide by nine rather than three, because area conversions square the linear factor. Getting that wrong produces an answer three times out, and it is the commonest mistake in area arithmetic.

For an irregular space, split it into rectangles, calculate each and add the results. That is more reliable than averaging an odd shape and it matches how the job actually gets measured.

How to use itStep by step05

How to use it

  1. Step 1: Pick the shape

    Rectangle, circle or triangle.

  2. Step 2: Enter the dimensions

    Length and width, or diameter for a circle, or base and height for a triangle.

  3. Step 3: Set the count

    For several identical areas.

  4. Step 4: Add waste separately

    Materials need an allowance on top. The material calculators apply it.

Example usageWorked figures06

Example usage

A room
20 by 14 ft is 280 sq ft — 31.11 sq yd, or 26.01 m².
A circular patio
A 16 ft diameter circle is 201.06 sq ft. Note the input is diameter, not radius, since that is what gets measured.
A gable end
A triangle 30 ft across and 6 ft high is 90 sq ft — the figure the siding calculator wants for a gable.
Frequently asked questionsCommon questions07

Frequently asked questions

How do I calculate square footage?

Length times width for a rectangle. For an irregular room, split it into rectangles, work out each and add them together.

How many square feet in a square yard?

Nine, not three. Area conversions square the linear factor, which is why a three-foot yard becomes a nine-foot square yard.

How do I measure an irregular room?

Divide it into rectangles along its natural lines, measure each separately and add the areas. Trying to average an odd shape introduces more error than the extra measurements cost.

Should I subtract for kitchen units or a fireplace?

Only for permanent built-ins covering meaningful area. Most fitters run flooring under appliances and keep a consistent perimeter, so deducting small obstructions tends to leave you short.

Does this include a waste allowance?

No — this is pure area. The material calculators apply waste, because the right allowance depends on the material and the layout.

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Browse every tool in Measurement & Conversion Calculators.