Use this page as an estimating workflow rather than a specification. Build the quantities in the order shown, use the linked calculators for the arithmetic, then verify every product-specific value against the material you intend to buy.
Calculate the sloping roof area
A pitched roof has more surface area than its horizontal footprint. Use the measured slope or calculate slope length from run and pitch for simple roof planes.
Use the tile rate for the chosen product
Tiles per square metre can vary with gauge and headlap. Use current product information rather than a universal rate.
Keep linear components out of the area calculation
Battens, ridge, verge and gutter are measured in linear metres or individual units. They should not be derived by simply multiplying roof area.
Break complex roofs into planes
Hips, valleys, dormers and extensions are easier to check when each plane is measured separately and then totalled.
Calculators for this job
- Roof Area Calculator
- Roof Tile Calculator
- Roof Batten Length Calculator
- Roofing Membrane Roll Calculator
- Guttering Length Calculator
Common mistakes
- Using plan area instead of sloping area
- Assuming every tile has the same coverage rate
- Forgetting overhangs or separate roof planes
- Using one waste factor for field tiles and linear components
Pre-order checklist
- Re-measure the main dimensions or compare them with a current drawing.
- Replace generic coverage, density, spacing or pack figures with the actual product data.
- Keep the base quantity, waste allowance and pack rounding as separate steps.
- Check whether any part of the job requires professional design, approval or a manufacturer-specific installation method.
- Save the raw measurements so the estimate can be reproduced if the supplier queries it.
The project planners deliberately stop at quantity planning. They do not certify structural adequacy, regulatory compliance or installation suitability.