Roof Tile Calculator 2026
Instantly estimate the number of roof tiles, felt underlay, battens, and ridge tiles needed for your project. Accounts for roof pitch, tile gauge, lap, and wastage.
Roof Dimensions & Tile Specs
Enter your roof measurements and choose your tile type
Horizontal length of the roof at the eaves (one slope)
Total width of the building from outer wall to outer wall
Angle of the roof slope in degrees (typical: 30°–45°)
How many sloped faces does the roof have?
Preset dimensions auto-fill below — adjust as needed
Vertical overlap between tile courses (typically 65–75mm for plain tiles)
Horizontal overlap between tiles in the same course
Add extra for cuts, breakages and ridge details
Standard breathable felt / underlay roll width
Material Estimates
Tiles, battens, underlay & ridge count
Enter your roof dimensions and tile type above, then click Estimate Roofing Materials to reveal your complete material list.
Common Tile Types & Coverage
Standard roof tile sizes, typical gauges, and approximate tiles per m² for the most popular UK roofing materials. Always add 10% for wastage and cuts.
| Tile Type | Size (mm) | Tiles per m² | Min Pitch | Typical Use |
|---|---|---|---|---|
| Plain Clay Tile | 265 × 165 | ~60 | 35° | Traditional / period homes |
| Concrete Plain Tile | 267 × 165 | ~60 | 35° | Modern & period replicas |
| Concrete Interlocking | 420 × 330 | ~10 | 17.5° | Modern housing estates |
| Natural Slate (Welsh) | 500 × 250 | ~24 | 20° | Heritage & conservation areas |
| Clay Pantile | 340 × 240 | ~14 | 15° | Eastern England, period barns |
Roofing FAQ
Answers to the most common questions about calculating roof tiles, battens, underlay, and pitch for DIY and professional roofing projects.
To calculate roof tiles, first find the total sloped roof area (eaves width × rafter length, adjusted for pitch). Then divide the area by the coverage area of a single tile (tile width minus side lap × tile length minus head lap). Always add 10% wastage for cuts and breakages.
Rafter length = (roof span ÷ 2) ÷ cos(pitch angle). Alternatively, multiply the horizontal run by the pitch factor for your angle. For example, a 35° pitch has a pitch factor of approximately 1.221, so a 4m run gives a rafter length of about 4.88m.
Minimum pitch depends on tile type. Plain clay tiles require a minimum pitch of 35°. Interlocking concrete tiles can go as low as 17.5°. Natural slate is typically laid at a minimum of 20°–25°. Always check the manufacturer’s specification for the specific tile you are using.
Roofing felt or breathable membrane is measured by the total sloped roof area plus a 150mm overlap on each horizontal run. As a rule of thumb, add 15% to the total roof area to account for laps, eaves, and verges. Felt typically comes in 1m-wide rolls of 20m or 50m length.
The number of batten rows equals the rafter length divided by the tile gauge (the exposed portion of each tile). Add one extra row for the eaves course. The total linear metres of batten needed is the number of rows multiplied by the full width of the roof (eaves width).