Square Footage Calculator

This is an estimate, not professional advice. Check your inputs and verify the result against your plans and local building code before you build or order. See terms and disclaimer.

How this calculator works

Choose the shape you are measuring, enter the dimensions in feet and inches, and the result updates instantly with the area in square feet, plus square yards and square meters. Each shape uses its own area formula, shown below. Add a waste allowance for flooring or tile, and a price per square foot to estimate cost. For an odd or L-shaped room, split it into rectangles, run each one, and add the results.

Worked example

A 12 ft × 10 ft room (Rectangle / Room shape), giving 120 square feet. Inputs: Length 12 ft, Width 10 ft, Number of rooms 1, Waste allowance 0 %. Result: 120 ft².

Square footage for common room sizes

Rectangle shape, no waste. Tap a size to load it in the calculator above.

Method & assumptions

Square footage is just area expressed in square feet, and the area depends on the shape. This calculator covers the shapes that come up in real projects. A room, lot or any rectangle is length times width. A square is one side multiplied by itself. A circle, a round patio or pool, is pi times the radius squared, where the radius is half the diameter. A triangle is half the base times the height when you have a right-angle height, or Heron’s formula when you only know the three side lengths. A border or frame, like the tiled edge around a room, is the outer rectangle minus the inner rectangle.

Measure in feet and inches the way you do on site; a measurement of 7 feet 3 inches is entered as 7.25 feet, because 3 inches is a quarter of a foot. Once you have the area in square feet, the calculator also shows square yards (divide by 9) and square meters (multiply by about 0.0929), since flooring, carpet and topsoil are often priced in those units. Add a waste allowance for anything you cut and fit: 5 to 10 percent is normal for flooring, tile and turf, more for diagonal layouts or busy patterns, because offcuts at the edges are unavoidable.

For an odd or L-shaped space, do not try to force it into one shape. Split it into rectangles and triangles, run each piece, and add the square footage together; subtract any opening or island you are not covering. Enter a price per square foot to turn the area straight into a material or labor cost, which is how flooring, paint, sod and concrete finishing are usually quoted. The figures here are geometric and exact, but always confirm the final order against supplier box sizes and coverage so you buy whole units.

Pro tips and common mistakes

• Enter inches as a decimal of a foot. A 12 foot 6 inch wall is 12.5 feet, because 6 inches is half a foot. The feet-and-inches fields do this for you, but it is worth knowing when you check the math.
• Split odd rooms into shapes. An L-shape is two rectangles; a room with a bay is a rectangle plus a triangle or part-circle. Calculate each piece and add them. It is faster and far more accurate than guessing one big rectangle.
• Add waste for flooring and tile. Plan 5 to 10 percent extra for cuts and breakage, and up to 15 percent for diagonal or herringbone layouts. You want full spare pieces from the same batch in case of repairs later.
• Subtract what you are not covering. For flooring, leave out a kitchen island base or a hearth; for paint, you might subtract large windows and doors. Run the opening as its own shape and subtract its area.
• Match the unit to the material. Carpet and vinyl are often sold by the square yard, topsoil and mulch by the cubic yard, paint by coverage per gallon. The square yard and square meter outputs save you a conversion at the store.

Frequently asked questions

References

• Area (Wikipedia)
• Heron’s formula (Wikipedia)
• Square foot (Wikipedia)

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