How this calculator works
Estimate roof surface area from a rectangular footprint and roof pitch, then convert area into roofing squares and approximate bundles.
Sloped area = footprint × pitch factor, where pitch factor = √(1 + (rise/12)²). Squares = area ÷ 100; bundles = squares × bundles per square.
Example
A 6:12 roof has a pitch factor of about 1.118, so its surface area is larger than the building footprint.
How to get a better estimate
- Hip roofs, valleys, dormers and multiple sections need separate measurements.
- Always verify bundle coverage for the selected shingle.
- Roof work is hazardous; measurements can often be taken from plans or professional reports.
What the result means
The result is a planning estimate. Dimensions, coverage, density, packaging and installation conditions vary by product and project. For purchasing, compare the result with the exact product label or supplier specification. For structural, electrical, code-regulated or safety-critical work, use an appropriately qualified professional.
Common questions about the Roofing Calculator
What does this calculator estimate?
Estimate roof surface area from a rectangular footprint and roof pitch, then convert area into roofing squares and approximate bundles.
What formula does it use?
Sloped area = footprint × pitch factor, where pitch factor = √(1 + (rise/12)²). Squares = area ÷ 100; bundles = squares × bundles per square.
How should I use the result?
Use it as a planning estimate, then verify the dimensions and replace editable defaults with the specifications for the product or service you actually intend to buy.