Roof Tile Calculator
Work out how many roof tiles or slates you need. Counts for plain tiles and slates are calculated from the size and headlap, so you can match your manufacturer’s specification instead of relying on a rule of thumb.
How many roof tiles do I need?
Roof tiles and slates per m²
At the default headlap for each type. Joints between slates are ignored, so allow a little extra.
| Tile or slate | Headlap | Gauge | Per m² | Minimum pitch |
|---|---|---|---|---|
| Plain tiles (265 × 165 mm) | 65 mm | 100.0 mm | 60.6 | 35° |
| Natural slate 600 × 300 mm | 75 mm | 262.5 mm | 12.7 | 20° |
| Natural slate 500 × 250 mm | 75 mm | 212.5 mm | 18.8 | 20° |
| Natural slate 400 × 200 mm | 75 mm | 162.5 mm | 30.8 | 20° |
| Large-format interlocking tiles | — | — | 10.0 | Product specific |
Slate minimum pitch is 20° only with sufficient headlap and slate length for the exposure; plain tiles need 35°.
Related
Frequently asked questions
How many roof tiles per m² do I need?
About 60 plain tiles per m² (265 × 165 mm at a 65 mm headlap), about 10 large-format interlocking tiles per m², and 13 to 31 natural slates per m² depending on slate size and headlap. Add 5–10% for cutting and breakages.
How do you calculate slates per m²?
Slates are double-lapped. The gauge (batten spacing) is (slate length − headlap) ÷ 2, and each slate covers gauge × width. Slates per m² = 1,000,000 ÷ (gauge × width) in millimetres. A 500 × 250 mm slate at a 75 mm headlap has a 212.5 mm gauge, so you need about 18.8 per m².
What headlap should I use?
Headlap depends on pitch and exposure. Plain tiles need at least 65 mm (75 mm for clay in severe exposure); slates need more at low pitches and on exposed sites. Use the slate or tile manufacturer’s table for your pitch and exposure zone.