Calculate Square Feet Calculator: Formula & Examples

To calculate square feet, multiply length by width when both are measured in feet, so a 12 by 10 foot room is 120 square feet. Squares, circles, triangles and L-shaped rooms each need a different formula or a bit of splitting into pieces, and the square footage calculator below does all six shapes at once, with the result also shown in square yards and square meters.

How to calculate square feet for a rectangle or room

For any rectangle or room, square footage is length times width, with both measurements in feet. A 12 by 10 foot bedroom is 12 x 10, which is 120 square feet.

Area (ft2) = Length(ft) x Width(ft)

Inches get entered as a decimal of a foot: 6 inches is 0.5 feet, so a wall measuring 12 feet 6 inches is 12.5 feet. Mixing feet and inches without converting is the most common source of a wrong total.

For a fast, error-free result across six different shapes, enter your dimensions in the square footage calculator, which also converts the area to square yards and square meters and can price it out per square foot.

Square footage for common room and lot sizes

Multiplying length by width gets tedious across several rooms or a full floor plan. The table below covers the sizes people look up most often.

Room size	Square feet	Square yards
10 x 10 ft	100	11.11
10 x 12 ft	120	13.33
12 x 12 ft	144	16.00
12 x 14 ft	168	18.67
14 x 16 ft	224	24.89
20 x 20 ft	400	44.44
24 x 24 ft	576	64.00

So a 12x12 room is 144 square feet, and a 10x10 room is 100 square feet. Those two sizes are the ones people search for most, since they match a typical bedroom and a small patio or shed pad.

How to calculate square feet for a square, circle or triangle

A square uses one measurement: side times side. A 10 foot square side is 10 x 10, or 100 square feet, the same result as a 10x10 rectangle.

A circle, like a round patio or fire pit pad, is pi times the radius squared, where the radius is half the diameter. A 12 foot diameter circle has a 6 foot radius, so the area is pi x 6 x 6, about 113.1 square feet.

Circle Area (ft2) = π x (Diameter ÷ 2)2

A triangle with a right-angle height is half of base times height. A 3 foot base with a 4 foot height gives 0.5 x 3 x 4, which is 6 square feet, the same triangle used in the classic 3-4-5 right-angle check. If you only know the three side lengths, Heron's formula solves it without a height measurement.

Once you have the square footage of a patio or slab area, the concrete calculator turns it into cubic yards and bags once you add the pour thickness.

How to calculate square footage of an L-shaped or irregular room

Do not try to force an L-shaped or irregular room into one formula. Split it into two or more rectangles, or a rectangle plus a triangle for a room with a bay window, and calculate each piece on its own.

Add the square footage of every piece together for the total. If there is an opening you are not covering, like a fireplace hearth or a kitchen island footprint, calculate that area separately and subtract it from the total.

This piece-by-piece method is exact, since it is built from the same length-times-width and area formulas used for simple shapes, just applied more than once.

A person using a laser measure across a patio while noting dimensions on a clipboard

Can I estimate square footage using Google Maps

Yes, but the two Google tools do different jobs. Google Maps measures straight-line distance between points, so you can trace a lot's length and width and multiply them for a rough estimate.

For an actual enclosed area, Google Earth's measure tool is built for it: you place points around the perimeter, close the shape back at the starting point, and it reads the square footage or square meters directly.

Both tools rely on satellite imagery and inferred property lines, so treat the result as a rough estimate, not a survey-grade measurement, especially near a property boundary.

Converting square feet to square yards, meters, and cost

Carpet, sod and some vinyl flooring are priced by the square yard, not the square foot. Divide square feet by 9 to convert, since one square yard is 3 feet by 3 feet, or 9 square feet.

For metric, multiply square feet by 0.092903 to get square meters. A 200 square foot room is about 18.6 square meters.

Once you have the area, multiply it by a price per square foot for a quick material or labor estimate, whether that is flooring, paint coverage or a concrete finish. The full set of concrete and masonry calculators picks up from there for slabs, block walls and paver patios sized by the square foot.

How we check this

Every formula is shown in full and verified with automated tests against manufacturer spec sheets and ASTM and ACI standards. We show our work so you can check it.

Frequently asked questions

How do I calculate the sq ft?

Multiply length by width, both in feet, for a rectangle or room: a 12 by 10 foot room is 120 square feet. For a square use side times side, for a circle use pi times the radius squared, and for an irregular room, split it into rectangles and add the pieces.

What is 12x12 ft in square feet?

A 12 by 12 foot area is 144 square feet, found by multiplying 12 by 12. For flooring or tile, add a 5 to 10 percent waste allowance, which brings the amount to buy up to roughly 151 to 158 square feet.

How big is 10x10 in sq ft?

A 10 by 10 foot area is 100 square feet, since 10 multiplied by 10 equals 100. That converts to about 11.1 square yards or 9.3 square meters.

Can I estimate square footage using Google Maps?

Google Maps itself measures straight-line distance between points, so you can trace a length and width and multiply them for a rough estimate. For a true enclosed-area reading, Google Earth's measure tool closes the shape and reports the square footage directly, though both are estimates based on satellite imagery, not survey measurements.

How do I convert square feet to square yards?

Divide the square footage by 9, since one square yard equals 9 square feet, a 3 by 3 foot square. So 180 square feet is 20 square yards, which is the unit carpet and some vinyl flooring are commonly priced in.

Calculate Square Feet Calculator: Formula for Any Shape

Key takeaways