Roof area
Estimate the sloped roof area from the plan size and the pitch.
Formula. plan area = length × width; roof area = plan area ÷ cos(pitch)
Assumptions
- Length and width are the horizontal plan, not the measurement up the slope.
- Pitch is in degrees from horizontal. A steeper roof has more surface than the plan.
- The roof is treated as a single plane over that rectangle. Hips, valleys and eaves overhangs are not drawn. Add overhangs into the plan size if you want them included.
- Pitch must be below 80 degrees so the formula stays meaningful. This does not price roofing.
Results are quantities. This calculator does not produce a price.