Square Footage Calculator — area from length and width

How it works

Square footage is simply the area of a rectangle — how much floor or ground a space covers:

area = length × width

Measure the length and width in feet and multiply them to get the area in square feet. The same rule works in any unit — metres give square metres, yards give square yards — as long as both sides use the same unit.

For rooms and plots that are not a single rectangle, break the shape into rectangles, calculate each one's square footage, and add them together. To subtract an opening (a kitchen island, a cut-out), work out its area the same way and take it off the total.

Worked example

A 12 × 10 ft room is 12 × 10 = 120 sq ft. A 24 × 24 ft two-car garage is 576 sq ft, and a 100 × 80 ft building plot is 8000 sq ft. If that room had a 3 × 5 ft closet bumped out, you would add its 15 sq ft for a total of 135.

Frequently asked questions

How do I calculate square footage?

Multiply the length by the width, both measured in feet: square footage = length × width. A 12-by-10-foot room is 120 square feet. For non-rectangular areas, divide them into rectangles, compute each, and sum the results.

What if my room is not a perfect rectangle?

Split it into rectangles. Measure and calculate the square footage of each part, then add them for the total. For alcoves or cut-outs, calculate their area and subtract it. Triangular sections are half of the enclosing rectangle (½ × base × height).

How do I convert square feet to square yards or square metres?

Divide square feet by 9 to get square yards (since 1 yard = 3 feet, 1 square yard = 9 square feet), or multiply square feet by 0.0929 to get square metres. Flooring is often sold by the square yard or square metre, so this conversion is handy.

How much extra should I buy for flooring or paint?

Add a waste allowance on top of the bare square footage — typically 5–10% for flooring and tile to cover cuts and mistakes, more for diagonal or patterned layouts. Calculate the exact area here, then multiply by 1.10 for a 10% buffer.

Does square footage include walls?

For flooring and paint you use the floor or wall surface area, not the wall thickness. Published "square footage" for a home usually measures the interior floor area. This calculator gives the area of whatever length and width you enter.

What units does the result use?

Whatever length unit you enter, squared. Feet give square feet, the usual unit for rooms and real estate in the US. Metres give square metres. Keep the length and width in the same unit and read the area in that unit squared.