Use the Roof Area Calculator to estimate a simplified roof quantity from building dimensions, pitch factor and waste. The tool shows its assumptions so you can change them rather than relying on a hidden market average.
Approximate roofing quantity——
Formula used
approximate roof quantity = plan area × pitch factor × (1 + waste allowance)
How to use the result
- Enter measurements or rates you can verify.
- Check the result for obvious unit mistakes.
- Save the assumptions with your project notes.
- Replace estimates with product data or real quotations as they become available.
Important limitations
- This is a simplified area model, not a roof survey
- Complex roofs need measured valleys, hips and separate planes
- Structural repair, access and materials are not priced by the quantity tool
Before you buy or sign
- Verify measurements on site
- Use product-specific coverage or waste guidance where available
- Confirm taxes, delivery, permits, labour and disposal separately when relevant
- For safety-critical or structural work, use an appropriately qualified professional
Why RepairCostPilot shows the assumptions
A calculator is useful only when you can see what drives the result. These tools deliberately use simple inputs and avoid pretending that one national figure is an exact local contractor price.