Roofing Calculator UK | How Many Roof Tiles Do I Need?
Free UK roofing calculator. Work out how many roof tiles, battens, felt and fixings you need from your roof dimensions. Covers concrete, clay and slate tiles.
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Results are estimates only and may vary depending on site conditions, material specifications and waste. EasyEstimate and its affiliates accept no responsibility for any loss or damage arising from reliance on these figures. Always verify quantities with your supplier before ordering.
How to Calculate Roof Tiles for a UK Roof
Ordering the right number of roof tiles saves money and avoids delays. The calculation depends on your roof area, tile type, and waste allowance. This guide covers the maths for the most common UK tile types.
The Formula
- Roof area = Floor area × pitch factor × number of sides
- Tiles needed = Roof area (m²) × tiles per m²
- Order quantity = Tiles needed × (1 + waste%)
Pitch Factor Table
The pitch factor converts horizontal area to the actual sloped roof area:
| Roof Pitch | Factor | Common Use |
|---|---|---|
| 15° | 1.04 | Low-pitch interlocking tiles |
| 22.5° | 1.08 | Minimum for many concrete tiles |
| 30° | 1.15 | Standard UK pitch |
| 35° | 1.22 | Common for plain tiles |
| 40° | 1.31 | Steeper traditional roofs |
| 45° | 1.41 | Period properties, slate |
| 50° | 1.56 | Steep period roofs |
Tiles Per m² by Type
| Tile Type | Tiles per m² | Typical Gauge | Min Pitch |
|---|---|---|---|
| Concrete interlocking (e.g. Marley Modern) | 10 | 345mm | 22.5° |
| Concrete interlocking (e.g. Redland 49) | 10 | 345mm | 22.5° |
| Large format slate effect | 9–10 | 340mm | 17.5° |
| Plain clay/concrete tile | 60–65 | 100mm | 35° |
| Natural Welsh slate (500×250mm) | 20 | 230mm | 25° |
| Natural Spanish slate (500×250mm) | 21 | 225mm | 25° |
| Rosemary clay tile | 60 | 100mm | 35° |
Worked Example: 8m × 6m Gable Roof at 30° Pitch
Using concrete interlocking tiles (10 per m²):
- Floor area = 8 × 6 = 48 m²
- Roof area = 48 × 1.15 (pitch factor) = 55.2 m²
- Two sides = 55.2 × 2 = 110.4 m² total roof area
- Tiles needed = 110.4 × 10 = 1,104 tiles
- Add 5% waste = 1,104 × 1.05 = 1,160 tiles
Battens
Roofing battens (typically 25×50mm or 25×38mm treated softwood) are laid horizontally at the tile gauge spacing:
| Tile Type | Batten Gauge | Battens per m² (linear m) |
|---|---|---|
| Concrete interlocking | 345mm | 2.9 lm |
| Plain tiles | 100mm | 10 lm |
| Natural slate | 225mm | 4.4 lm |
For the example above: 110.4 m² × 2.9 = 320 linear metres of batten + 10% waste = 352 lm
Underlay / Felt
Roofing underlay is laid in horizontal courses with a 150mm overlap:
- Underlay per m² = roof area × 1.15 (to allow for 150mm laps)
- For the example: 110.4 × 1.15 = 127 m² of underlay
Standard rolls are 1m × 15m (15 m²) or 1m × 50m (50 m²).
Ridge and Hip Tiles
| Component | Calculation |
|---|---|
| Ridge tiles | Ridge length ÷ 0.3m per tile |
| Hip tiles | Hip length ÷ 0.3m per tile |
| Valley tiles/trays | Valley length ÷ 0.3m per tile |
| Verge clips | Rafter length ÷ batten gauge × 2 verges |
Fixings
- Tile clips/nails: Every tile in exposed areas; every 5th course in sheltered areas (check BS 5534)
- Batten nails: 2 per batten intersection with rafter
- Ridge fixings: Mechanical dry fix systems are now required under BS 5534
From Roof Tiles to a Full Roofing Estimate
This guide gives you material quantities. A complete roofing estimate also includes:
- Labour (typically £30–50/m² for re-roofing in 2026)
- Scaffolding (usually £500–1,500 for a standard house)
- Skip hire for old tiles
- Lead work for flashings and valleys
- Insulation if upgrading to current standards
EasyEstimate’s roofing calculators handle all of these items with live UK pricing — materials, labour, plant, and a complete schedule you can send to your client or supplier.
Try the full roofing calculator free →
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Frequently Asked Questions
- How many roof tiles per square metre in the UK?
- It depends on the tile type. Concrete interlocking tiles typically need 10–12 per m², plain clay tiles need 60–65 per m², and natural slates need 20–30 per m² depending on size. Always check the manufacturer's stated coverage rate.
- How do I calculate the area of my roof?
- Measure the horizontal floor area and multiply by the pitch factor. For a 30° pitch, multiply by 1.15; for 40° multiply by 1.31; for 45° multiply by 1.41. For a gable roof, multiply by 2 (two sides). For a hip roof, measure each face separately.
- How much batten do I need for a tiled roof?
- Divide the rafter length by the batten gauge (spacing), then multiply by the roof width. Add 10% for waste. For concrete interlocking tiles with a 345mm gauge on a 6m rafter, that's approximately 17 rows of battens per side.
- What waste allowance should I add for roof tiles?
- Allow 5% for a straightforward rectangular roof with simple gable ends. Allow 7.5–10% for roofs with hips, valleys, dormers, or complex geometry where more cutting is required.
- How many ridge tiles do I need?
- Divide the ridge length (in metres) by 0.3m (standard ridge tile length including joint). A 10m ridge needs approximately 33 ridge tiles. Add 2–3 spares.
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