How to use it
- Enter roof length and width in meters.
- Enter a pitch multiplier of at least 1.
- Choose a waste percentage and calculate.
Roofing Calculator
Estimate roof material area using a supplied pitch multiplier.
Important: This calculator provides material estimates only. It is not structural, safety, legal, or building-code advice. Always confirm with a qualified professional before construction.
About the Roofing Calculator
This material-area estimator applies an entered pitch multiplier and waste percentage to a rectangular roof footprint.
Estimation formula
Flat area equals length × width. Adjusted area equals flat area × pitch multiplier, and the waste percentage is then added.
Example
An 80 m² footprint with a 1.12 multiplier estimates 89.6 m² before waste and 98.56 m² after 10% waste.
Notes
This is material-area arithmetic only. It does not assess roof design, loading, access, installation, drainage, safety or code requirements.