Building & renovation
How do you calculate real roof area from floor plan and pitch?
Real roof area from footprint and pitch — optional membrane or tile pack estimate.
Quick answer
Roofing materials are ordered by real sloped area, not the house footprint on the plan. For a simple gable or shed roof, slope correction is footprint ÷ cos(pitch): a 30° pitch adds about 15% area versus flat projection. Complex hips, valleys and dormers need a site measure — this is a planning estimate for regular rectangles.
Advanced settings
Real roof area
88.3 m┬▓
For regular gable or shed roofs: real area = footprint ├À cos(pitch). Complex hips, valleys and dormers need a site measure ÔÇö this is a planning estimate only.
How it works
Optional material mode converts m² into pack counts using rough yields (membrane 1:1, tiles ~10 m²/pack, shingles ~3 m²/pack) — always verify with your supplier’s sheet size. Safety first on ladders and roofs; product links like roof waterproof membrane are for planning purchases, not installation shortcuts.
Frequently asked questions
How do I measure roof pitch?+
Use a smartphone inclinometer on the slope, or rise ÷ run: 3 m rise over 10 m run ≈ 16.7°. The calculator accepts common presets (15–45°) or a custom angle in the pitch field.
Footprint 8×10 m at 25° — what area?+
Footprint = 80 m². cos(25°) ≈ 0.906 → real area ≈ 80 ÷ 0.906 ≈ 88.3 m² before waste. Add 10% for cuts and overlaps on membrane or shingles.
Does this work for hip roofs?+
Not accurately — hips and valleys change true area versus a single rectangle. Use this for ballpark budgeting on simple roofs; order materials after a roofer’s measure or detailed plan for complex shapes.
Membrane vs tiles quantity — which to trust?+
Membrane is often sold by m² roll width — our 1:1 mode is close. Tiles and shingle packs vary wildly by profile and overlap; treat pack count as ±15% until you have the supplier datasheet.
As an Amazon Associate I earn from qualifying purchases — the price does not change for you.
More calculators — Building & renovation
- Real cost per m²
- Interior paint
- Facade paint
- Wood varnish
- Wood impregnant
- Floor lacquer
- Metal enamel
- Metal primer
- 2K floor paint
- Bonding primer
- Fixative primer
- Window trim enamel
- External wall insulation
- Microcement
- Marmorino
- Venetian plaster
- Radiator spray paint
- Drywall / plasterboard
- Floor protection rolls
- Spray foam
- Car paint 2K
- Sandblasting media
- Torch membrane propane
- Sandblast compressor
- Airless sprayer
- Drywall sander
- Tile cutter
- Demolition hammer
- Cement mixer
- Scaffold tower
- EPS hot wire cutter
- Floor grinder
- Floor edger
- Concrete grinder
- Scissor lift