Roof Area Calculator
Calculate roof surface area and squares from plan dimensions and pitch.
Enter your project details
Each dimension can use its own unit—for example feet for length and inches for thickness. Package counts are rounded up.
Formula and calculation steps
Roof surface = plan area × pitch multiplier × (1 + waste)- Plan area is 120 ft².
- Pitch 4:12 produces a 1.054× multiplier.
- Convert surface to squares and round packages up.
Worked example
Use this for a fast area and squares check when bundles and trim are not required.
How to use this calculator
- Enter plan length and width.
- Set roof pitch.
- Read surface area and squares.
Example: Use this for a fast area and squares check when bundles and trim are not required.
Questions about this calculator
Plan area or surface area—which do I enter?
Enter horizontal plan dimensions; pitch converts them to roof surface area.
When should I use the shingle calculator instead?
Use the shingle calculator when you also need bundles, ridge caps and starter strips.
Can I use mixed units?
Yes. Choose feet, inches, metres or centimetres and the calculator converts each input before calculating.
Is this a final material order?
No. Confirm drawings, product coverage, local code and site conditions before buying or building.
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<iframe src="https://www.buildcalclab.com/embed/roof-area-calculator/?theme=light" width="100%" height="640" title="BuildWise calculator" style="border:0;max-width:720px"></iframe>Assumptions and references
Results are estimates based on the dimensions and values you enter. Verify final quantities, manufacturer coverage and site-specific requirements before ordering.
Last reviewed: July 2026 · Read our calculation methodology