Roof materials
Roof tiles
Tile and full-pack quantities from entered roof area and product coverage data.
How to use this calculator
Prepare measurements and product data
Measure slope area in m². Read tiles per m² and pieces per pack for the exact model. Consumption may depend on batten gauge and laps; do not derive it solely from gross tile dimensions. Calculate different products separately.
Formula and rounding
Planned tiles = area × tiles per m² × (1 + allowance / 100). Round tiles up, then packs = round up(tiles / tiles per pack).
Worked example
Illustrative inputs: 80 m² roof area, 10 tiles/m², 10% allowance and 30 tiles per pack. These values do not specify a product.
| Stage | Calculation |
|---|---|
| Tiles before allowance | 80 × 10 = 800 |
| Plan with allowance | 800 × 1.10 = 880 |
| Full packs | 880 / 30 ≈ 29.33 → 30 packs |
| Purchase and surplus | 900 tiles; 900 − 880 = 20 |
The result means 30 packs of 30, or 900 tiles. The extra 20 tiles arise from pack rounding and are compared with the plan already including allowance.
Check before buying
- Consumption matches the established gauge and laying conditions.
- A pack contains a positive whole number of tiles.
- Special tiles and accessories have a separate purchase list.
Limitations
The estimate covers field tiles. It does not lay out courses, select fixings, or include ridge, verge, ventilation or penetration units. Area-based rounding does not replace roof setting out.
Questions and answers
Why round pieces before packs?
A tile is indivisible, while a pack is the purchase unit. For 880 tiles and packs of 30, 29 packs provide only 870, so 30 packs are needed.
Can I use another tile model's consumption?
No. Size, gauge, laps and laying conditions belong to a specific product. Use the data for the variant you intend to purchase.
Sources and scope
- Marley — Roofing Sitework Guide, batten gauge, pp. 60–61
Product-specific setting out between eaves/ridge battens and separate fixed points. The simple quantity calculator is not that setting-out method.
- NIST — SI Units: Area
Square metres and area-unit notation; not an installation or cutting rule.
Manufacturer data relates tile consumption to a particular gauge and laps. Our example uses 10 tiles/m² and 30 tiles per package to demonstrate the arithmetic; these are not specifications of a linked product. For an order, obtain both values for the exact tile model and the gauge specified for your roof.