Worked example
Single room
- Input
- 12 ft × 10 ft
- Output
- 120 ft²
Both dimensions are already in feet, so no conversion is needed.
Square Footage Calculator
Use this sq ft calculator or sqft calculator by entering each shape with one consistent unit. The calculator converts every area to a common base, adds them, and then displays the total in your chosen unit.
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How to use this calculator
Choose a shape for the first area.
Enter its measured dimensions and add more areas if needed.
Read the total in square feet, square meters, or another available area unit.
Formula
Rectangle: A = length × width. Triangle: A = base × height ÷ 2. Circle: A = π × radius². Total area is the sum of all shapes.
Worked example
A 12 ft × 10 ft rectangle plus an 8 ft × 6 ft rectangle has an area of 120 + 48 = 168 ft².
Reference guide
Formula details and result guidance
Follow the variables, derivation, precision rule, and worked cases below to reproduce the calculation independently.
Variables
| Symbol | Meaning | Unit | Role |
|---|---|---|---|
| L | Measured length | selected length unit | Input |
| W | Measured width | selected length unit | Input |
| A | Rectangular area | square unit | Output |
Derivation
- For each rectangle, multiply perpendicular dimensions: A = L × W.
- Convert each partial area to square feet before addition; a linear conversion factor k becomes k² for area.
- For a composite floor plan, total area is ΣAi after subtracting any excluded rectangles.
Rounding and precision
The engine keeps unrounded partial areas and converts before summing. The display rounds square feet to 2 decimal places; procurement should use a separately chosen waste allowance.
Worked and boundary examples
Worked example
Two-zone plan
- Input
- 8 ft × 6 ft plus 4 ft × 3 ft
- Output
- 60 ft²
Add 48 ft² and 12 ft² only after treating the zones as separate rectangles.
Boundary case
Zero-width sketch
- Input
- 10 ft × 0 ft
- Output
- 0 ft²
A zero width has no rectangular area; confirm that the measurement was not omitted.
Common mistakes
- Applying a linear feet-to-meters factor directly to an area instead of squaring the factor.
- Adding lengths from separate zones before multiplying, which changes the geometry of the plan.
- Treating calculated floor area as a material order without accounting for cuts, defects, or pattern layout.
How to interpret the result
The result is the 2-dimensional area represented by the entered rectangles. It does not infer wall thickness, slope, openings, waste, or a survey boundary.
Scope
Appropriate for
- Checking a measured rectangular room or floor zone.
- Combining simple rectangles for an early material estimate.
Do not use for
- Certifying a legal property area or survey.
- Ordering material without field measurements and a project-specific waste plan.
Tools for the same task
Next tools in the workflow
Evidence and sources
- A rectangle has area equal to length L multiplied by width W.National Institute of Standards and Technology: Circumference, Area and VolumeSupports: Standard plane-geometry and solid-geometry relationships. Reviewed 2026-08-22.
- Area conversions apply the square of the corresponding length conversion.National Institute of Standards and Technology: Guide for the Use of the International System of Units (SI)Supports: SI unit symbols, decimal prefixes, unit conversion, and reporting conventions. Reviewed 2026-08-22.
Assumptions and limits
- Dimensions describe flat geometric shapes.
- All dimensions are converted before areas are added.
- No waste allowance is applied by default.
Sources
- National Institute of Standards and Technology: Circumference, Area and VolumeArea and volume formulas for common geometric shapes. Reviewed 2026-08-14.
- National Institute of Standards and Technology: Unit ConversionExact unit conversion and final-result rounding guidance. Reviewed 2026-08-14.
Related calculators
Verification
How this calculator is checked
Trust comes from reproducible evidence, not model confidence. You can inspect the formula, assumptions, worked example, and cited sources on this page.
- Versioned calculationFormula logic is kept separate from the interface and covered by automated registry and behavior checks.
- Cited evidenceSources linked for independent checking: 2.
- Transparent AI useAI may assist drafting or adversarial review. Agreement between models is not proof, and no human expert review is claimed unless a named reviewer is shown.
Frequently asked questions
How do I calculate an irregular space?
To learn how to work out sqft, split an irregular space into rectangles, triangles, or circles, calculate each part, and add the areas. Measure cutouts separately and subtract them before ordering.
Can I use metric and US customary units in the Square Footage Calculator?
Yes. Unit changes convert the same canonical measurement; they do not reinterpret or round your original value.
When does the calculator round?
The calculation keeps full precision internally and rounds only the displayed result. Whole packages are rounded up at the final step.
Last updated 2026-08-25 · 1.0.0 · 1.0.0 · Published by YunFanLabs