Count tiles, battens and ridge
Tiles = roof area × tiles per m². Battens = roof area ÷ gauge. Coverage figures are typical — change them to match the product's data sheet.
Typical figures for estimating. Gauge, headlap, minimum pitch and fixings come from the manufacturer's data and the site exposure — check before you order.
Tiles per m² — typical coverage
Typical manufacturer figures at the gauge shown. Battens per m² = 1,000 ÷ gauge in mm.
| Tile / slate | Per m² | Battens m/m² | Min pitch* |
|---|---|---|---|
| Plain tile 265 × 165 mm (clay or concrete) | 60 | 10.0 | 35° |
| Large interlocking tile 420 × 330 mm, 75 mm headlap | 9.9 | 2.9 | 22.5° |
| Large interlocking tile 420 × 330 mm, 100 mm headlap | 10.7 | 3.1 | 17.5° |
| Small interlocking tile approx. 380 × 230 mm | 16.3 | 3.3 | check |
| Natural slate 500 × 250 mm, 75 mm headlap | 18.8 | 4.7 | check |
| Natural slate 500 × 250 mm, 100 mm headlap | 20 | 5.0 | check |
| Natural slate 600 × 300 mm, 100 mm headlap | 13.3 | 4.0 | check |
*Minimum pitch for smooth tiles as published for those formats; slate minimums depend on the slate size, headlap and exposure, so check the manufacturer's tables. Fittings (eaves, verge, hip and valley) are extra.
How to estimate roof tiles
1. Get the slope area
Measure each roof slope along the rafter, or take the plan area and multiply by the pitch factor (1 ÷ cos pitch). A 40 m² plan at 35° is 48.8 m² of slope — the roof pitch calculator does this for you.
2. Tiles per m² from the gauge
Gauge is the batten spacing: the tile length less the headlap. Tiles per m² = 1 ÷ (gauge × cover width). For natural slates, gauge = (slate length − headlap) ÷ 2, so a 500 × 250 slate at a 75 mm headlap is laid at 212.5 mm, about 18.8 slates per m².
3. Add waste
Allow at least 5% for breakages and cutting on a plain gable roof; hips, valleys and dormers mean more cuts, so allow more.
4. Battens and ridge
Battens per m² = 1,000 ÷ gauge (mm): 10 m per m² for plain tiles at 100 mm and about 2.9 m for large interlocking tiles at 345 mm. Ridge and hip tiles are counted from their length — a 450 mm ridge laid end to end needs about 2.2 per metre.
Questions roofers ask
How many plain tiles per m²?
About 60 per m² for a standard 265 × 165 mm plain tile at a 100 mm gauge, with 10 linear metres of batten per m². Check the gauge on the manufacturer's data sheet.
How many interlocking tiles per m²?
Large-format interlocking tiles (around 420 × 330 mm) cover roughly 9.9 per m² at a 75 mm headlap and 10.7 at 100 mm. Smaller interlocking tiles around 380 × 230 mm are about 16 per m².
How many slates per m²?
A 500 × 250 mm natural slate needs about 18.8 per m² at a 75 mm headlap and 20 at 100 mm. A 600 × 300 mm slate at 100 mm headlap needs about 13.3 per m².
How much waste should I allow on roof tiles?
At least 5% on a simple roof for breakages and cuts. Roofs with hips, valleys and dormers need more because of the cut tiles.
More free tools for roofers
Roof pitch calculator — degrees, rafter length, pitch factor› All free calculators for the trades›Every roof documented, every extra paid
Dated photo evidence per job, quotes from the scaffold, signed extras, scaffold inspections and live job costing.
See Graftum for roofersTypical figures for estimating; check gauge, headlap and minimum pitch with the manufacturer.