Square Footage Calculator
Calculate square footage for rectangular, square or circular areas and convert the result to square yards and acres.
Your project details
Change the inputs below to match your project.
How this calculator works
The calculator converts simple shape dimensions into square feet, square yards and acres. Use it for measured project areas such as rooms, patios, landscape beds and flooring zones.
Formulas used
| Shape | Formula |
|---|---|
| Rectangle | Length × width |
| Square | Side × side |
| Circle | π × (diameter ÷ 2)² |
Worked examples
| Shape | Dimensions | Area |
|---|---|---|
| Rectangle | 20 × 15 ft | 300 sq ft |
| Square | 12 × 12 ft | 144 sq ft |
| Circle | 12 ft diameter | ≈113.1 sq ft |
For irregular spaces
Break the project into simple shapes, calculate each section separately and add them together. For an L-shaped room, two rectangles are usually easier to measure and audit than one rough outline.
Measured area versus purchase quantity
Square footage tells you the geometric area. Flooring, tile, paint and landscape materials may need project-specific allowances for cuts, pattern matching, coats, overlap or waste. Keep measured area separate from the allowance so you can see how the purchase quantity was built.
Common mistakes
- Mixing inches and feet without converting
- Using house floor area as roof area
- Ignoring closets or alcoves that receive the material
- Subtracting openings twice
- Adding waste before confirming measured area
Where to use the result next
Send the measured area to the Flooring Calculator, Paint Calculator, Mulch Calculator or Cubic Yard Calculator, depending on the project.
FAQ
How many square feet are in one square yard?
9 square feet.
How many square feet are in one acre?
43,560 square feet.
Should I round the measurement?
Keep the measured area as precise as practical, then round the final purchase quantity based on package sizes or supplier increments.