Roofing Calculator

The Roofing Calculator estimates base roof area, pitch-adjusted area, and ordering area from building length, width, pitch factor, and waste percentage.

Calculation method

The tool calculates the footprint and then applies a pitch factor to account for the slope. Finally, a waste allowance is added.

$\text{Base area}=\text{Length}\times\text{Width}$ $\text{Roof area}=\text{Base area}\times\text{Pitch factor}$ $\text{Order area}=\text{Roof area}\times\left(1+\frac{\text{Waste}}{100}\right)$

Worked example

For a 12 m by 8 m footprint, pitch factor 1.15, and 10% waste:

1. Base area: 12 x 8 = 96 m2.
2. Pitch-adjusted area: 96 x 1.15 = 110.4 m2.
3. Order area: 110.4 x 1.10 = 121.44 m2.

Frequently Asked Questions

What is a pitch factor?

It is a multiplier that approximates the sloped roof surface relative to the footprint. A value based on the roof pitch or a measured surface area should be used.

Does this calculate roof squares?

No. Divide the order area by the material's coverage to calculate bundles, sheets, or squares.

Does it include valleys and edges?

No. Complex geometry, dormers, hips, valleys, and ridges require separate measurements.

Limitations

This is a rectangular-footprint estimate. Quantities should be confirmed with a roofing professional and product coverage data.