Roofing Calculator
Calculate the actual roof surface area, accounting for its pitch (slope).
Calculate
Enter your values below.
Result
Roof surface area
0
Formula used
Roof area = Footprint area ÷ cos(pitch)
Example: 120 m² footprint at a 30° pitch → roof area ≈ 138.6 m².
How to use this calculator
- Enter Building footprint area (m²), Roof pitch (degrees from horizontal).
- Press Calculate to see your result instantly.
FAQ
Frequently asked questions
Why is roof area larger than the footprint?
A sloped roof has more actual surface area than the flat ground area it covers — the steeper the pitch, the bigger the difference.
What if my roof is flat (0° pitch)?
The roof area will equal the footprint area exactly.
How do I find my roof's pitch in degrees?
Roof pitch is often given as a rise/run ratio (e.g. 6:12) — convert with arctan(rise/run) to get degrees.
Does this account for overhangs?
No, add any eave overhang area to your footprint first for a more complete estimate.