📐 Roof pitch factor (1 ÷ cos)
A sloped roof is always bigger than the footprint it covers. Multiply the horizontal area by this factor:
| Pitch |
15° |
25° |
30° |
35° |
45° |
| Factor | 1.035 | 1.103 | 1.155 | 1.221 | 1.414 |
🏠 Coverage cheat-sheet
| Material |
Coverage |
| Asphalt shingles (standard) | 3 bundles = 1 square = 100 sq ft ≈ 9.29 m² |
| #15 felt underlayment | ~37 m² (4 squares) / roll |
| Frankfurter Pfanne | ~10 / m² · Latte ~32 cm |
| Doppelmuldenfalzziegel | ~15 / m² · Latte ~33 cm |
| Biberschwanz (Doppeldeckung) | ~36 / m² · Latte ~15.5 cm |
📐 How it is calculated
Roof area = (length + 2·overhang) × (width + 2·overhang) ÷ cos(pitch), then × (1 + waste). Shingles: convert to squares (÷ 9.29 m²) and multiply by bundles per square; underlayment and ridge caps are rounded up per roll/bundle. Tiles: area × tiles per m²; battens = area ÷ batten spacing (the spacing follows the tile type!); ridge tiles ≈ 3 per metre of ridge.
✍️ Worked example
House 10 × 8 m with 0.5 m overhangs and a 30° gable roof: footprint 11 × 9 = 99 m², roof area 99 ÷ cos 30° = 114.3 m², with 10% waste 125.7 m². Shingles: 13.5 squares × 3 = 41 bundles, 4 rolls of #15 felt, 2 ridge cap bundles. Tiles (Frankfurter Pfanne, 10/m²): 1,258 tiles, ~393 m of battens and 33 ridge tiles for the 11 m ridge.
💡 Pro tips
- Hips and valleys cut a lot of material — use 15% waste or more on complex roofs.
- Premium and designer shingles often take 4–5 bundles per square instead of 3 — check the wrapper.
- The batten spacing depends on the tile: plain Biberschwanz tiles need battens roughly every 15 cm, twice as many as interlocking tiles.
- Not included here: starter strip, drip edge, nails, counter-battens and ridge vent — add them to your order.
🌍 Naming around the world
Roof = techo / techumbre = Dach = 屋根 = 지붕 · Shingle = tejuela asfáltica = Bitumschindel · Roof tile = teja = Dachziegel = 瓦 = 기와 · Pitch = pendiente = Dachneigung · Ridge = cumbrera / caballete = First · Batten = listón = Dachlatte · Underlayment = fieltro / membrana = Unterspannbahn.
❓ Frequently Asked Questions
How many bundles of shingles do I need?
Work out the real roof area (footprint ÷ cos of the pitch), add ~10% waste, convert to squares (1 square = 100 sq ft ≈ 9.29 m²) and multiply by 3 bundles per square for standard shingles. A 10 × 8 m house with 0.5 m overhangs and a 30° pitch needs about 13.5 squares → 41 bundles.
How does the roof pitch change the area?
A sloped roof is bigger than its footprint by the factor 1 ÷ cos(pitch): +3.5% at 15°, +10% at 25°, +15% at 30°, +22% at 35° and +41% at 45°. The calculator applies the factor automatically from the pitch you enter.
How many roof tiles per m²?
It depends on the tile model: large interlocking tiles like Frankfurter Pfanne take about 10 per m², Doppelmuldenfalzziegel about 15 per m², and plain tiles (Biberschwanz) in double coursing around 36 per m². The batten spacing follows the tile — about 32 cm for large tiles but only ~15.5 cm for Biberschwanz.