Reviewed, sourced guidance
Roof tile coverage, gauge and headlap
Direct answer
Tile quantity equals sloped roof area multiplied by the coverage rate for the chosen product and laying specification. The rate is not universal: one Marley tile page lists 9.9 tiles per m² at 75 mm headlap and 10.7 at 100 mm.
A tile’s physical size does not tell you its installed coverage. Use the exact manufacturer data for its headlap, pitch and finish.
Key takeaways
- Use a coverage rate for the exact product rather than a generic tile type.
- Headlap can change the tile count per square metre.
- Pitch and exposure can change the permitted laying detail.
- Field-tile coverage excludes fittings and accessories.
Use exact product data
Manufacturer estimators and data sheets can tie a product choice to a material take-off. Russell Roof Tiles, for example, structures its estimator around tile choice, colour, dimensions and materials.
Check the document date and the product name before copying a coverage value into an estimate.
- Record the product name and finish.
- Record the headlap and gauge that apply.
- Keep the source link beside the calculated count.
Sources for this section: Russell Roof Tiles, Tile Estimator (observed 2026-09-25)
A manufacturer example shows why
Marley lists Duo Modern coverage at 9.9 tiles per m² with 75 mm headlap and 10.7 with 100 mm headlap.
Its page also distinguishes minimum pitch by finish and headlap. Those values are not defaults for other tiles.
- Smooth finish: 22.5 degrees at 75 mm headlap on the listed product.
- Smooth finish: 17.5 degrees at 100 mm headlap on the listed product.
- Granular finishes have different stated minimum pitches.
Sources for this section: Marley, Duo Modern product data (observed 2026-09-25)
Count fittings separately
A field-tile count does not include ridge, hip, valley, verge or eaves units. Measure those details using the chosen system’s own component guidance.
Long slopes and severe exposure can need additional technical advice, as the Marley product page notes for its named systems.
- Do not treat a field-tile count as a complete roof order.
- Check accessories, fixings and ventilation components against the same product system.
- Ask the manufacturer or a competent roofer about non-standard details.
Sources for this section: Marley, Duo Modern product data (observed 2026-09-25)
Next steps
- Enter the exact tile coverage in the calculator.
- Measure fittings separately and confirm the fixing specification.