How many roof tiles per m²?

Roughly 60 for small plain tiles, about 10 for concrete interlocking, and around 20 for many natural slates. But real coverage depends on the product's gauge and lap. Always use the manufacturer's table.

How do I calculate roof pitch?

Pitch in degrees is the angle whose tangent is rise ÷ run (half-span). Example: rise 2.5m and run 4m → tan⁻¹(0.625) ≈ 32°. Many UK house roofs sit between about 30° and 45°.

How do I work out roof area from plan size?

Multiply plan (ridge) length by the slope length for one side, then double for a duo-pitch roof. Do not use the flat plan area alone: that understates the tiled surface.

What waste percentage for roof tiles?

5% is common on simple rectangular roofs. Use 8–10% or more where there are hips, valleys, dormers or many cuts. Ridge, hip and verge fittings are ordered separately.

Does tile type change batten spacing?

Yes. Batten gauge is set by the tile manufacturer's fixing spec and the roof pitch. This calculator estimates tile count only: set battens from the product data sheet.

Free Roof Tile Calculator

Estimate roof pitch, roof area and how many tiles you need from plan size and rise or slope length. Free for UK roofers, no sign-up, answer in seconds.

This roof tile calculator works out pitch, roof area and tile quantity from plan length and either slope length or rise + half-span, for plain, concrete interlocking or slate tiles. Coverage figures are typical UK values: always confirm with the tile manufacturer's fixing specification.

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Roof Tile Calculator results

Fill in the details and select Calculate to see your figures.

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How to use the Roof Tile Calculator

1Enter the ridge/plan length of the roof.
2Either enter the slope (rafter) length, or rise + half-span so pitch and slope are calculated.
3Choose one side (lean-to) or both sides (duo-pitch).
4Pick tile type and a waste allowance (5% simple, more for hips/valleys).
5Confirm final quantities with the manufacturer's coverage table for your lap and gauge.

How the Roof Tile Calculator works

Roof area is plan length times slope length (times two for a duo-pitch). Pitch comes from rise over run.

pitch° = atan(rise ÷ run) × 180/π → area = plan × slope × sides → tiles = area × tiles/m² × (1+waste%)

Rise 2.5m, half-span 4m → slope = √(2.5²+4²) = 4.72m; pitch ≈ 32°.
Plan length 8m, both sides: area = 8 × 4.72 × 2 ≈ 75.5 m².
Concrete interlocking at 10/m² with 5% waste: 75.5 × 10 × 1.05 ≈ 793 tiles.
Order by full packs and allow extras for ridges, hips and valleys separately.

Coverage depends on lap and gauge. Minimum pitch varies by tile product. Confirm with the tile manufacturer's fixing specification before ordering.

Typical UK benchmarks

Plain tiles per m²	Typical small plain tiles ~60/m²
Concrete interlocking per m²	Typical ~9.7–10/m²
Natural slate per m²	Varies by size and gauge: often ~20/m²

Disclaimer

This tool gives an estimate for general guidance only, based on typical UK figures and the details you enter. It is not a formal quote, survey, or professional advice. Always confirm with a qualified tradesperson before relying on any figure, as regional prices, site conditions, and current standards vary.

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