Using the Roofing Calculator
Enter footprint length and width in meters, including the overhang you want covered. Pitch is entered as rise per twelve units of horizontal run: a 6-in-12 pitch uses a rise of 6. The output also converts the result to roofing squares.
Worked example
Use the example inputs below to reproduce this result. These are the form's starting values, not recommended targets. Changing your inputs updates your result above; this worked example stays fixed for comparison. Results are rounded for display.
Example inputs
- Length (m)
- 5
- Width (m)
- 4
- Roof rise per 12 units of run
- 6
- Waste allowance (%)
- 10
Example result
- Estimated roof area (m²)
- 24.596748
- Roofing squares (100 ft²)
- 2.6475719
Method and assumptions
Footprint × √(1 + pitch²), plus waste. Assumes a uniform pitch; include overhang in footprint and measure complex roofs separately.
Turn an estimate into an order
A geometric quantity is a starting point for purchasing. Check whether the supplier sells by bag, box, mass or bulk volume, and use the stated coverage or yield to convert the result. Round only after accounting for the chosen allowance and packaging increments. For irregular spaces, divide the job into simpler sections and combine quantities with the same units.
Common question
What is a roofing square?
A roofing square is 100 square feet of roof area. It is an area unit, not a count of shingles or bundles. Use the product's stated coverage to convert the calculated squares into a purchase quantity.
Guide updated .