Square Footage Calculator
Calculate the square footage of up to five rectangles, triangles, circles, trapezoids, or L-shaped areas. Enter dimensions, then add an optional waste allowance and price per square foot.
Add Up the Area of a Room, Floor, or Lot
Square Footage Formula
Where:
- \(A\), \(B\), \(C\), and \(D\) — the dimensions required by the selected shape, converted to feet before calculating.
- \(A_i\) — the area of one shape in square feet; \(A_{\mathrm{total}}\) — the sum of all selected areas.
- \(w\) — waste allowance as a percentage; \(p\) — price per square foot.
Each shape has its own area formula. The calculator adds the shapes first, then applies the waste allowance and, if a price is entered, estimates the cost.
Square Footage – Calculation Example
Example: the default settings describe one rectangular room that is 12 ft long and 10 ft wide, with 0% waste and a price of $5 per square foot.
\[ A_{\mathrm{total}}=12\times10=120\ \mathrm{sq\ ft} \]
\[ A_{\mathrm{with\ waste}}=120\left(1+\frac{0}{100}\right)=120\ \mathrm{sq\ ft},\qquad \mathrm{cost}=120\times\$5=\$600 \]
Result: 120 sq ft of area, 120 sq ft including waste, and an estimated total cost of $600.00.
How to use the calculator
- Use Add another area to select from 1 area to 5 areas. Select more than one if you need to add separate rooms or sections.
- Under each Area, choose a Shape: Rectangle, Triangle, Circle, Trapezoid, or L-shape (two rectangles). The calculator shows the measurements that shape needs.
- Enter Length / base 1 / diameter (A) and, when shown, Width / base 2 / height (B), Height / length 2 (C), and Width 2 (D). Choose the Unit beside each measurement; you can mix ft, in, yd, m, and cm.
- Set Waste allowance if you want to include extra material. Enter a Price per square foot for a cost estimate, or clear that field to omit the estimate.
- Read Total area for the measured footprint, Area including waste for the adjusted quantity, and Area breakdown to check each shape separately.
What square footage tells you
Square footage measures the size of a two-dimensional surface in square feet. A 12 ft by 10 ft rectangle covers 120 sq ft; its perimeter is a different measurement and cannot tell you its area by itself. Square footage is useful for comparing room sizes, estimating flooring coverage, or measuring a lot divided into simpler shapes.
This calculator reports the same total area in square feet, square yards, square meters, and acres. These are unit conversions, not four different measurements: 9 sq ft equals 1 sq yd, and 43,560 sq ft equals 1 acre. The acre result is rounded to six decimal places, so very small areas may display as 0.000000 acres.
The Area including waste result is a planning quantity rather than an increase in the surface itself. For example, adding 10% waste to a 120 sq ft floor gives 132 sq ft to budget for cuts and offcuts; the floor still measures 120 sq ft. The estimated cost multiplies this adjusted quantity by the entered price, so it changes when either the waste allowance or price changes.
Measurement tips and limitations
- For a triangle, enter its base as A and its perpendicular height as B. A sloped side is not the height unless it meets the base at a right angle.
- For a circle, A is the full diameter across its center, not the radius. The calculator does not use B for a circle.
- For a trapezoid, A and B are the two parallel bases; C is the perpendicular distance between them.
- For an L-shape, measure two non-overlapping rectangles: A × B and C × D. If they overlap, their shared portion will be counted twice. An irregular space can also be divided into separate shapes using Add another area.
Measure the surface you actually intend to cover. For flooring, exclude openings or fixed features only if they will not be covered and the difference matters to your estimate. A 10% waste allowance is a common flooring starting point, but the right amount depends on the product, layout, cuts, and installation method. This calculator does not account for package sizes, minimum order quantities, labor, or tax.
Area alone does not give the amount of a material with thickness or depth. Once you know a ground area, use the gravel calculator or mulch calculator for a depth-based estimate. For wall coverings, the wallpaper calculator addresses roll coverage rather than floor area.
Frequently Asked Questions
How do I calculate square footage by hand if my measurements include feet and inches?
Convert each measurement to feet before multiplying. Divide the inches by 12 and add that to the feet: 10 ft 6 in becomes 10.5 ft. A rectangular room measuring 10 ft 6 in by 8 ft 3 in is 10.5 × 8.25 = 86.625 sq ft. Keep the decimal places until the final step to avoid rounding errors.
How do I convert square inches to square feet?
Divide the number of square inches by 144, because one square foot contains 12 × 12 = 144 square inches. For example, 1,800 sq in ÷ 144 = 12.5 sq ft. Do not divide an area by 12; that converts inches to feet only when you are working with a single length.
What is a normal square footage for a bedroom?
Many bedrooms are roughly 100–200 sq ft, but there is no single size that suits every home or purpose. A smaller room may still fit a bed, while furniture, walkways, and storage affect how usable it feels. If you need to know whether a room legally qualifies as a bedroom, check local building and real estate rules rather than relying on its area alone.
How do I subtract a closet, opening, or other uncovered area?
Calculate the area to exclude separately, then subtract it from the larger area by hand. For example, a 150 sq ft floor with a 12 sq ft section that will not be covered has a net area of 138 sq ft. This calculator adds entered shapes; it does not treat an additional shape as a cutout. Apply any material allowance to the net area.
How many boxes of flooring do I need for my square footage?
Divide the required square footage, including any planned extra material, by the coverage printed on one box, then round up to a whole box. If you need 132 sq ft and each box covers 23 sq ft, you need 6 boxes. Check whether the product is sold only in full boxes and confirm its actual coverage before ordering.
Is square footage the same as linear footage?
No. Square footage measures a surface, while linear footage measures distance along a line. Flooring is commonly priced by square foot; baseboards are commonly measured by linear foot. To estimate baseboards, add the lengths of the walls where they will be installed and account for doorways as appropriate. You cannot convert between the two units without another measurement, such as material width.
Should I use floor-plan dimensions for a sloped ceiling or roof?
Use the dimensions of the surface you intend to cover. A floor plan gives the horizontal footprint, which is smaller than the actual surface area of a sloped roof or ceiling. For a simple rectangular slope, measure its length along the slope and multiply by its width. For complex roofs, measure each plane separately and account for openings or overhangs as needed.