Roof Tile Calculator — How Many Tiles Do I Need?

It depends on the tile type. Common concrete interlocking tiles (including ‘large format’ types like Marley Edgemere, 420×330mm, and Redland Renown, 418×330mm) need approximately 10 tiles per m² at a 100mm headlap, plain clay plain tiles need around 60 per m² (because of their small 265×165mm size and double-lap), and natural or artificial slates need about 20 per m² for the common 500×250mm size at a 100mm lap. A few genuinely oversized concrete tiles such as the Forticrete SL8 cover at roughly 8 per m². Coverage always varies with headlap/gauge, so check the manufacturer's stated coverage rate for your specific tile and lap. If you only know the plan dimensions, use our Roof Area Calculator to convert to actual sloping roof area first.

Allow 10% wastage for most tile types (concrete interlocking, slate, large format). For plain clay tiles, allow 15% because they require more cutting at hips, valleys and verges. If your roof has a complex shape with many hips and valleys, consider increasing wastage to 15-20%.

Use the 'Enter roof area' input method. Measure or calculate the sloping area of each plane separately (main slopes, hip ends, lean-to sections and so on), add them together and enter the total. Because tiles are ordered per square metre, the combined area gives an exact tile count no matter how many planes the roof has or what shape they are; the length × rafter option is just a shortcut for a simple two-sided gable. Our Roof Area Calculator converts plan dimensions and pitch to sloping area for each plane. For shapes with many hips and valleys, raise the wastage allowance to 15-20%, because more tiles are cut at the joins.

Single-lap tiles (like concrete interlocking) overlap on one edge and the top — they need fewer tiles per m². Double-lap tiles (like plain clay) overlap on both sides and top/bottom, providing better weather protection but needing significantly more tiles. Plain clay tiles typically require 60 per m² compared to just 10 for concrete interlocking.

It is not recommended to mix different tile types on the same roof slope as they have different profiles, gauges and weights. However, you can use ridge tiles, hip tiles and valley tiles that are designed to work with your main tile type. Use our Hip Tile Calculator and Ridge Tile Calculator to estimate quantities for these accessories.

Yes. Different tiles have very different weights — clay plain tiles laid at 60/m² weigh roughly 65–77 kg/m², while large format concrete interlocking tiles such as Marley Edgemere weigh about 44–48 kg/m² (47.5 kg/m² at a 100mm headlap per the Edgemere data sheet). Always use the manufacturer's stated weight for your tile. If switching tile type, your roof structure may need strengthening. A structural engineer should check the rafters, purlins and wall plates can support the new load. Use our Roof Truss Calculator to estimate truss quantities for new builds. You will also need felt and battens — see our Felt and Batten Calculator.