Square Footage Calculator
Select a shape, enter your measurements, and instantly get the area and volume. Add depth to calculate cubic feet for concrete, mulch, soil, and gravel. Supports both Imperial and Metric units.
Measuring Rooms and Spaces
Knowing the square footage of a room is one of those practical skills that comes up more often than you'd think. Whether you're buying carpet, planning a furniture layout, or listing a property, the measurement drives real decisions with real money attached.
For a standard rectangular room, measuring is straightforward: grab a tape measure, get the length and width in feet, and multiply. A bedroom that's 12 feet by 10 feet has 120 square feet of floor space. If the room isn't perfectly rectangular — maybe there's a closet alcove or an angled wall — break it into simpler shapes, calculate each one, and add them together.
When measuring, always measure at floor level and take the longest dimensions. Don't assume opposite walls are the same length, because in older homes especially, rooms can be surprisingly out of square. Measure both pairs of walls and use the average if they differ. For accuracy to the nearest inch, convert inches to decimals of a foot: 6 inches is 0.5 feet, 3 inches is 0.25 feet, 9 inches is 0.75 feet.
A common mistake is confusing square feet with linear feet. If someone says a room is "12 by 10," those are linear measurements in feet. The square footage is the product: 120 sq ft. When you're buying baseboard molding, you need the perimeter (linear feet): 12 + 10 + 12 + 10 = 44 linear feet. When buying flooring, you need the area (square feet): 120 sq ft, plus typically 10% extra for waste and cuts.
Circular spaces come up in gardens, pools, and architectural features like rotundas. Measure the diameter across the widest point, divide by 2 to get the radius, and use the formula pi times radius squared. A circular patio with a 10-foot diameter has a radius of 5 feet and an area of about 78.5 square feet.
Converting Between Square Feet and Other Units
Once you have your area in square feet, you'll often need to convert to other units depending on the context. Real estate listings in the US use square feet, but international markets and scientific applications use square meters. Rural land is measured in acres.
The conversions aren't hard, but the numbers aren't intuitive either. One square meter equals about 10.764 square feet. Going the other way, one square foot is roughly 0.0929 square meters. A 1500 square foot apartment is about 139 square meters. If you're browsing property listings in Europe, knowing this conversion lets you compare sizes meaningfully.
Acres are used for land parcels. One acre equals 43,560 square feet, which is about the size of a football field (minus the end zones). A quarter-acre lot — common in suburban neighborhoods — is 10,890 square feet. A half-acre is 21,780 square feet. To put it in perspective, a typical suburban lot might be 60 feet by 182 feet (10,920 sq ft), which is just over a quarter acre.
Hectares are the metric equivalent of acres. One hectare equals 10,000 square meters or about 2.471 acres. Farmers, land planners, and environmental scientists outside the US typically use hectares.
Here are some rough benchmarks to help you visualize sizes. A single-car garage is about 200 square feet. A typical one-bedroom apartment ranges from 500 to 750 square feet. The average American home is around 2,300 square feet. A tennis court is 2,808 square feet. An NBA basketball court is 4,700 square feet. An Olympic swimming pool covers about 13,455 square feet. Having these reference points makes it much easier to picture what a number like "1,200 square feet" actually feels like in person.
How to Measure Irregular Shapes
Real-world spaces don't always come in neat rectangles and perfect circles. L-shaped rooms, oddly angled lots, and curved garden beds require a bit more creativity, but the underlying principle is always the same: break the irregular shape into regular shapes, measure each one, and add the areas together.
An L-shaped room is the most common irregular shape in homes. Mentally divide it into two rectangles. Measure each rectangle's length and width, calculate both areas, and add them. If the room is 15 feet by 10 feet on one side and extends another 8 feet by 6 feet, the total is (15 × 10) + (8 × 6) = 150 + 48 = 198 square feet.
For rooms with a bump-out or bay window, measure the main rectangle first, then add the area of the bump-out as a separate shape. If the bump-out is a half-circle (like some bay windows), its area is half of pi times radius squared.
Free-form shapes like garden beds or ponds can be approximated using the grid method. Lay out a grid of 1-foot squares over the area (or draw it on graph paper from measurements). Count the full squares, then estimate the partial squares. This isn't precise, but for landscaping purposes it's close enough to order the right amount of mulch or sod.
For truly irregular land parcels, surveyors use a method called triangulation. They divide the property into triangles, measure the sides, and use Heron's formula to calculate each triangle's area. The sum gives the total lot area. Modern surveying equipment with GPS can do this automatically, but the mathematical principle is the same one you'd use with a tape measure and graph paper.
A practical tip: when you need to measure a large outdoor area and you don't have a 100-foot tape measure, pace it off. The average adult walking stride is roughly 2.5 feet. Count your paces, multiply by your stride length, and you'll get a surprisingly decent estimate.
Square Footage in Real Estate
In real estate, square footage is arguably the single most important number in any listing. It directly affects the listing price, the appraised value, property taxes, and how quickly a home sells. Understanding how it's measured — and how it can be misrepresented — can save you thousands of dollars.
What counts as "living space" varies by jurisdiction. Generally, heated and finished areas count: bedrooms, living rooms, kitchens, bathrooms, and hallways. Garages, unfinished basements, attics, and covered porches usually don't count, even if they're usable space. A finished basement might or might not count depending on local conventions and whether it has proper egress (exit) windows.
The American National Standards Institute (ANSI) standard for measuring residential square footage says to measure from the exterior walls and include only finished areas above grade (above ground level). But not everyone follows ANSI. Some agents measure from interior walls, which gives a smaller number. Others include finished basements, which gives a larger number. Always ask how the measurement was taken before comparing listings.
Price per square foot is the standard metric for comparing home values within a market. If homes in a neighborhood sell for $200 per square foot and a 1,500 sq ft house is listed at $350,000, that's $233 per square foot — which might indicate premium features or an overpriced listing. Context matters, of course: a renovated kitchen, a good school district, or a waterfront view can justify a higher price per square foot.
Buyers should be aware of the "phantom square footage" problem. A listing says 2,000 square feet, but the actual living space is 1,700 because the agent included the garage or measured generously. This happens more than it should. If the square footage drives your purchase decision, measure it yourself or hire an appraiser. The cost of an independent measurement is trivial compared to overpaying for a home.
Area & Volume Formulas
Rectangle: A = L × W | Circle: A = πr² | Triangle: A = ½ × b × h | Volume: V = A × depth
The area of a rectangle is length times width. The area of a circle is pi times the radius squared. The area of a triangle is one-half times the base times the height. To get volume, multiply the area by the depth. This turns a rectangle into a box (rectangular prism), a circle into a cylinder, or a triangle into a triangular prism. Volume is essential for estimating materials like concrete, mulch, soil, and gravel. One cubic yard equals 27 cubic feet, which is the standard unit for ordering bulk materials.
Where:
- L = Length of the rectangle
- W = Width of the rectangle
- r = Radius of the circle
- b = Base of the triangle
- h = Height (perpendicular) of the triangle
- d = Depth for volume calculation
Example Calculations
Rectangular Room
Calculating the area of a 12 ft by 10 ft room.
Area = length × width = 12 × 10 = 120 sq ft. Converting to square meters: 120 × 0.0929 = 11.15 sq m. Converting to acres: 120 / 43,560 = 0.002755 acres. This is a typical small bedroom or home office.
Circular Patio
Calculating the area of a circular patio with a 5-foot radius.
Area = π × r² = 3.14159 × 5² = 3.14159 × 25 = 78.54 sq ft. This 10-foot diameter circle is about the size needed for a small round dining table with chairs and walking space.
Frequently Asked Questions
One acre contains exactly 43,560 square feet. An acre is roughly the size of a football field without the end zones (which is 48,000 sq ft). A quarter-acre residential lot — very common in American suburbs — is 10,890 square feet, which could be a lot measuring about 66 feet by 165 feet.
Multiply the square footage by 0.0929 to get square meters. For example, 1,000 sq ft equals about 92.9 square meters. Going the other way, multiply square meters by 10.764 to get square feet. A quick mental shorthand: divide square feet by 10 and subtract a bit, so 1,000 sq ft is roughly 100 minus a little, giving about 93 square meters.
It depends on how the measurement is taken. The ANSI standard for residential real estate measures from the exterior face of exterior walls, so wall thickness is included in the total. Interior measurements taken from wall to wall within each room give a smaller number since they exclude wall thickness. For practical purposes like buying flooring, measure the interior dimensions — that's the actual usable floor area.
Divide the L-shape into two rectangles. Measure the length and width of each rectangle, calculate both areas (length times width), and add them together. For example, if one section is 15 ft by 10 ft and the other is 8 ft by 6 ft, the total is 150 + 48 = 198 square feet. Be careful to choose the dividing line so the two rectangles don't overlap or leave a gap.
Most flooring professionals recommend buying 10% more than the calculated square footage. This accounts for cutting waste, pattern matching, and potential mistakes during installation. For diagonal installations or rooms with many angles and doorways, consider ordering 15% extra. Natural materials like hardwood may have some unusable pieces due to defects, so the extra material provides a buffer.