How many roof tiles do I need per m²?

It depends on the tile type. Concrete interlocking tiles need approximately 10 tiles per m², plain clay tiles need around 60 per m² (due to their smaller size and double-lap), natural or artificial slates need about 20 per m², and large format concrete tiles need roughly 8 per m². Always check the manufacturer's stated coverage rate for your specific tile. If you only know the plan dimensions, use our Roof Area Calculator to convert to actual sloping roof area first.

How much wastage should I allow for roof tiles?

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%.

What is the difference between single and double lap tiles?

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.

Can I mix tile types on a UK roof?

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. Always check with the tile manufacturer for compatible accessories.

Do I need to check my roof structure before re-tiling?

Yes. Different tiles have very different weights — plain clay tiles can weigh 70-80 kg/m² while large format concrete tiles weigh around 40-45 kg/m². 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.

Roof Tile Calculator — How Many Roof Tiles Do I Need per m2?

Roof Tile Calculator — How Many Tiles Do I Need?

Calculate how many roof tiles you need for any UK roof. Covers concrete interlocking, plain clay, slate and large format tiles with wastage allowances.

Input Method

Tile Type

Total Roof Area

Total sloping area of roof (both sides for a gable)

Include wastage allowance

Adds 10% extra for cuts and breakages

Wastage Percentage

10% recommended for Concrete Interlocking

Price Per Tile (optional)

Enter your supplier price for a cost estimate

How We Calculate This

Our roof tile calculator works by multiplying your total roof area by the coverage rate for your selected tile type, then adding an appropriate wastage allowance. Coverage rates are based on standard UK tile sizes and manufacturers' installation guidelines.

The formula

Tiles needed = Roof area (m²) × Tiles per m² × (1 + Wastage %)

If entering dimensions, roof area is calculated as: Length × Rafter length × 2 (for both sides of a standard gable roof).

Coverage rates used

Concrete Interlocking: ~10 tiles/m² (e.g. Marley Mendip, Redland 49)
Plain Clay: ~60 tiles/m² (double-lap, e.g. traditional handmade or machine-made)
Natural/Artificial Slate: ~20 tiles/m² (standard 500×250mm at gauge)
Large Format Concrete: ~8 tiles/m² (e.g. Marley Edgemere, Redland Renown)

Wastage allowances

Standard wastage is 10% for most tiles to cover cutting at verges, hips and valleys. Plain clay tiles have a higher 15% default because the smaller tile size means more cuts. For complex roof shapes, you may want to increase the wastage further.

Frequently Asked Questions

Last updated: February 2026

All calculations are estimates. Verify with your supplier.

Roof Tile Calculator — How Many Tiles Do I Need?

How We Calculate This

The formula

Coverage rates used

Wastage allowances

Frequently Asked Questions

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