Calculate how many roof tiles, ridge tiles, and battens you need
Whether you are re-roofing an entire house, building an extension, or replacing damaged tiles after a storm, knowing how many roof tiles you need before ordering is essential. Over-ordering ties up money and leaves you with pallets of surplus tiles to store or return. Under-ordering is worse -- a half-finished roof exposed to the weather while you wait for the next delivery can cause serious damage to timbers, insulation, and ceilings below. Roof tiles are sold by the pallet or by the square metre, and the number you need depends primarily on the tile type. Concrete interlocking tiles, the most common choice on UK housing estates, cover the largest area per tile at roughly 10 tiles per square metre. Plain tiles (whether concrete or clay) are much smaller and require approximately 60 per square metre, giving a more traditional appearance but significantly increasing labour and material costs. Natural and man-made slates sit between the two at around 20 per square metre. This calculator handles all three types and includes ridge tiles and batten requirements so you can produce a complete materials list in one go. When ordering roof tiles in the UK, always check that your chosen tile meets the requirements of BS 5534 (the British Standard for slating and tiling). Your local Building Control officer will check compliance as part of any building regulations application, and using non-compliant tiles can invalidate your roof warranty and insurance cover.
To calculate the number of roof tiles you need: 1. Enter the roof length in metres. This is the ridge length -- the horizontal distance from one gable end to the other (or the total length of the ridge line on a hipped roof). If your roof has multiple sections, calculate each section separately and add the totals. 2. Enter the roof width (slope length) in metres. This is the distance measured along the slope from the eaves (bottom edge) to the ridge (top). If you only have the horizontal span, you can convert it using: slope length = span / cos(pitch angle). For a typical 35-degree pitch, multiply the horizontal span by 1.22. 3. Select the tile type from the dropdown. Concrete interlocking tiles are the most common and economical choice. Plain tiles give a more traditional look but require many more tiles. Slate offers a premium appearance and long lifespan. 4. Adjust the waste allowance using the slider. The default 10% is suitable for simple rectangular roofs with few cuts. Increase to 15% or more for roofs with hips, valleys, dormers, or skylights where more cutting and waste is generated. 5. Review the results. The calculator shows the total number of tiles needed (with and without waste), the number of ridge tiles required, and the total length of tile battens in metres. Use these figures to prepare your order with your builders merchant or tile supplier.
The roof tile calculation is based on the roof area and the coverage rate of the chosen tile type: Roof area = roof length (m) x roof width along slope (m) For a 10m x 5m roof: area = 50 square metres. Tiles needed = roof area x tiles per square metre. For concrete interlocking tiles at 10 per m2: 50 x 10 = 500 tiles. For plain tiles at 60 per m2: 50 x 60 = 3,000 tiles. For slate at 20 per m2: 50 x 20 = 1,000 tiles. Tiles with waste = tiles needed x (1 + waste percentage / 100). With 10% waste on 500 tiles: 500 x 1.10 = 550 tiles. Ridge tiles are calculated at one per 300mm of ridge length. A 10m ridge requires ceil(10 / 0.3) = 34 ridge tiles. Standard concrete ridge tiles are 450mm long with a 150mm overlap, giving an effective 300mm per tile. Batten requirements depend on the tile gauge (the exposed portion of each tile row). Concrete interlocking tiles have a gauge of approximately 340mm, plain tiles around 100mm, and slate approximately 200mm. Batten rows = ceil(slope length / gauge), and total batten length = batten rows x ridge length. Each row requires one continuous run of 25x50mm treated softwood batten across the full width of the roof.
All tile coverage rates are approximate and based on standard UK tile sizes. Always check the specific coverage rate stated by the tile manufacturer, as it can vary between products. For clay plain tiles, some manufacturers quote 60 tiles per m2 while others quote 64 per m2 depending on the exact tile dimensions and recommended gauge. Roof pitch affects the choice of tile -- most concrete interlocking tiles require a minimum pitch of 17.5 degrees, while plain tiles can go down to 35 degrees minimum. Natural slate is suitable for pitches as low as 20 degrees with appropriate headlap. Building Regulations Approved Document B (fire safety) may impose additional requirements on tile type for properties near boundaries. Your chosen tile must also meet wind uplift requirements under BS 5534, which may require mechanical fixing (nailing or clipping) of every tile in exposed locations.