Square Footage Calculator

Calculate area for rectangles, circles, triangles and multiple rooms.

Your area will appear here.

About the Square Footage Calculator

Measuring a room or surface usually starts with lengths, but most materials are sold by area. This calculator turns dimensions for floors, walls, lots and common shapes into square footage or another square unit that can be carried into a material estimate.

For irregular spaces, the cleanest approach is to divide the shape into simple sections, calculate each section separately and add the areas. Trying to force an irregular room into one rectangle often creates more error than the calculator itself.

How to Use the Square Footage Calculator

  1. Choose the shape that best matches the section you measured, such as a rectangle or circle.
  2. Enter the measured dimensions in the units shown. Use finished dimensions if the result is for finished surface coverage.
  3. For an irregular space, calculate separate simple sections and add them rather than estimating one oversized rectangle.
  4. Use the resulting square footage as the net area; add material-specific waste separately when planning purchases.

How the Calculation Works

For a rectangle, area = length × width. A circle uses area = πr², while other supported shapes apply their corresponding geometric formulas. Dimensions are converted to compatible units before multiplication.

Area units are squared units, so converting feet to metres is not the same as converting square feet to square metres. The calculator applies the correct area conversion to the final geometric result.

Worked example

Square Footage Calculator Worked Example

12 ft × 15 ft room

Multiply length by width: 12 × 15 = 180. The room has 180 square feet of floor area. If flooring requires a 10% allowance, the purchasing quantity would be 180 × 1.10 = 198 ft², but that allowance belongs to the material estimate rather than the geometric area itself.

Result guide

Understanding Your Square Footage Calculator Result

Square footage describes surface area, not how much material you should automatically purchase. Tile, flooring, roofing and other materials need their own waste, package-size and layout considerations.

Before you rely on the answer

Assumptions and Limitations

  • Dimensions are measured along the relevant finished surface.
  • The selected geometric shape reasonably represents the section being measured.
  • Material waste and offcuts are not part of net square footage unless added separately.

Practical tip

Using This Result in Practice

For rooms with alcoves or missing sections, sketch the space and label each measurement. A simple drawing makes it easier to see which areas should be added and which openings should be subtracted.

Related calculations

Useful Calculations to Continue With

If the area is for a floor purchase, continue with the Flooring Calculator to include waste and material quantity.

For tile work, use the Tile Calculator after finding the net area so box quantities and tile dimensions can be considered.

Authoritative references

Useful Official Sources

For standards, definitions or real-world guidance related to this calculation, these primary sources may be useful:

Common questions

Square Footage Calculator FAQ

How do I calculate square footage for an L-shaped room?

Split the room into two rectangles, calculate length × width for each one and add the two areas.

Should I subtract cabinets or fixed furniture?

Only if those areas will definitely not receive the material you are estimating. For flooring installations, confirm the installer’s preferred measuring method.

Is square footage the same as linear feet?

No. Square feet measure area, while linear feet measure length. A product sold by linear foot needs a separate conversion based on its width.