Square Footage Calculator
This square footage calculator measures rectangles, squares, circles, triangles and borders, and adds as many of them as you need into one total. Enter each dimension in feet, inches, yards or meters (you can mix them), and you get the total in square feet, square yards, square meters and acres. Add a price per square foot and it gives you the total cost too.
How to calculate square footage
Multiply the length by the width, both in feet. A 12 by 16 foot room is 192 square feet.
Square feet = length in feet × width in feet
Other shapes have their own formula, and the calculator has a setting for each:
- Split the space into shapes. An L-shaped room is two rectangles; a round patio is a circle.
- Add one area per shape. A circle takes its diameter, a triangle its base and height, and a border its outer and inner sizes, which suits a path around a lawn or a frame of tile.
- Enter inches or meters as they are. Each box has its own unit. For dimensions like 12 feet 7 inches, the square footage calculator with feet and inches takes both at once.
- Read the total in square feet, square yards, square meters and acres.
For curved or ragged outlines, the calculator for rooms with multiple shapes and cutouts adds trapezoids and cut-outs and averages a ragged edge. Every shape is worked through in how to calculate square footage, and what is a square foot explains the unit itself.
Living area from outside dimensions
A house the size of the median new US home (2,142 sq ft) loses about 99 square feet as a one-story and 139 square feet as a two-story when it's measured inside its 2x6 exterior walls instead of outside them: 4.6% and 6.5% of its living area. A room-by-room total falls short of an ANSI-based appraisal by at least that much from the exterior walls alone, because the ANSI home measurement standard measures from the outside of the exterior walls.
| Median new house, 2,142 sq ft | 2x4 walls (4.5 in) | 2x6 walls (6.5 in) |
|---|---|---|
| One-story | 69 sq ft (3.2%) | 99 sq ft (4.6%) |
| Two-story | 97 sq ft (4.5%) | 139 sq ft (6.5%) |
How we worked it out. 2,142 sq ft is the median new single-family house completed in 2025, per the Census Bureau. We drew it as a square, the shape with the least wall for its area, so a longer or L-shaped plan loses more; the two-story is two equal 1,071 sq ft floors. Each wall is the stud plus drywall and sheathing, as exterior wall thickness explains. ANSI also measures outside the siding, which isn't counted here, so a real house usually loses more.
Appraisers follow the ANSI Z765 measurement standard, and gross living area explains the figure that ends up on an appraisal. Gross vs net square footage covers the difference between outside and inside measurements, and how square footage is measured in real estate explains why a listing, a tax record and an appraisal can disagree.
Square footage chart
Square feet convert to other units with one factor each, from NIST's conversion tables.
Back again: × 10.764.
1 acre is 43,560 sq ft.
12 × 12 inches in a sq ft.
Common room sizes in square feet and square meters
| Room size | Square feet | Square meters |
|---|---|---|
| 8 x 10 ft | 80 | 7.4 |
| 10 x 10 ft | 100 | 9.3 |
| 10 x 12 ft | 120 | 11.1 |
| 12 x 12 ft | 144 | 13.4 |
| 12 x 14 ft | 168 | 15.6 |
| 12 x 16 ft | 192 | 17.8 |
| 14 x 16 ft | 224 | 20.8 |
| 15 x 15 ft | 225 | 20.9 |
| 16 x 20 ft | 320 | 29.7 |
| 20 x 20 ft | 400 | 37.2 |
| 24 x 24 ft | 576 | 53.5 |
The full square footage chart adds garage, building and lot sizes. Typical sizes by room are in standard room sizes, average bedroom size and closet dimensions.
Every calculator, by job
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Embed this calculator on your site
Flooring stores, builders and print shops can put this calculator on their own pages for free. Paste the code into any page or block that accepts HTML, and the calculator grows to fit as customers add areas.
- Please keep the credit line under the calculator.
- If your site builder strips the script, the calculator still works at a fixed 820 pixel height and scrolls inside its frame.
- Want it narrower? Change the 640px maximum width; the fields stack into one column on small screens.
Need a version with your own default units or a different calculator from the list above? Ask through the contact page.
What counts in a home's square footage
A home's official square footage is its finished, above-grade area. Fannie Mae's summary of ANSI Z765-2021 reports below-grade space separately and requires a ceiling of at least 7 feet in finished area.
Reported as below-grade area, however well it's finished. See does a basement count.
At least half the floor needs a 7 foot ceiling, and nothing under 5 feet counts. See does a finished attic count.
Not part of finished square footage, with one exception: a garage fully converted into living space. See does a garage count.
Only a four-season room that's open to the house, on permanent heat and finished like the other rooms counts; three-season rooms don't. See does a sunroom count and Florida room.
Room by room rules are in what counts as square footage. Check that two listings were measured the same way before you compare their price per square foot. Offices and shops lease on rentable area, which adds a share of common space, as commercial square footage explains.
Frequently asked questions
How do you calculate square footage?
Multiply length by width in feet: a 10 by 12 room is 120 square feet. For a space made of several shapes, work out each one and add them; the calculator does this when you add another area.
How do you calculate square footage with inches?
Divide the inches by 12 and add them to the feet before you multiply, so 10 feet 6 inches is 10.5 feet. If both sides are in inches, multiply them and divide by 144.
How many square feet is a 12x12 room?
144 square feet, which is about 13.4 square meters.
Can I add up more than one room at once?
Yes. Add each room as its own area and the calculator keeps a running total, which works for a whole floor plan or an L-shaped room.
How do you find the square footage of an irregular shape?
Split it into rectangles, triangles and circles, work out each one and add them, subtracting any cut-outs. The irregular shape calculator also averages widths along a curved edge, and the how to calculate square footage guide shows each method.
How much square footage do the walls add to a house?
For a house the size of the median new US home, 2,142 square feet, measuring outside rather than inside 2x6 exterior walls adds about 99 square feet on one story and 139 on two, or 4.6% and 6.5%. Appraisals under ANSI Z765 use the outside measurement.
Can I put this calculator on my website?
Yes, for free. Copy the embed code from the embed section into your page and keep the credit line under it.
How big is a square foot?
A square 12 inches on each side, which is 144 square inches or about 0.093 square meters.