Construction/Home calculator
Roofing Calculator
Estimate roof surface area from plan area, pitch factor, and waste allowance.
Formula
Roofing area estimate
Roof estimates depend on pitch, hips, valleys, overlaps, local codes, and installer recommendations.
Roof area = plan area x pitch factor x (1 + waste %)
100 sq m plan area with 1.12 pitch factor and 10% waste needs about 123.2 sq m.
FAQs
What is pitch factor?+
Pitch factor adjusts flat plan area to the sloped roof surface area.
Does this estimate shingles or sheets?+
It estimates surface area, which can then be converted to your chosen material coverage.
How does the Roofing Calculator calculate the result?+
It uses the Roofing area estimate: Roof area = plan area x pitch factor x (1 + waste %). 100 sq m plan area with 1.12 pitch factor and 10% waste needs about 123.2 sq m.
What information do I need to use the Roofing Calculator?+
Estimate roof surface area from plan area, pitch factor, and waste allowance.
How accurate is the Roofing Calculator?+
Roofing Calculator applies the formula and assumptions shown on this page. Results may be rounded for readability, so verify changing rates, thresholds, medical guidance, or legal rules with the cited source or a qualified professional.
What should I check before using the Roofing Calculator result?+
Check that the units, dates, rates, and assumptions match your situation. Change one input at a time to understand which values have the largest effect on the result.
Construction/Home guide
How to use the Roofing Calculator
Estimate roof surface area from plan area, pitch factor, and waste allowance. The page also explains the roofing area estimate and shows a practical example: 100 sq m plan area with 1.12 pitch factor and 10% waste needs about 123.2 sq m.
- 1
Enter your details
Enter plan area, pitch factor, and waste allowance, then complete any other fields shown in the calculator.
- 2
Check the calculation
Review the result alongside the roofing area estimate: Roof area = plan area x pitch factor x (1 + waste %).
- 3
Compare scenarios
Change one or more inputs to see how they affect the roofing Calculator result before you use the estimate.
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