Roofing Calculator
Calculate the actual sloped roof surface area from its footprint and pitch, for ordering roofing material.
- Free to use
- Accurate results
- No registration required
- Works on all devices
Enter your roof's footprint dimensions and slope angle to find its actual sloped surface area.
Your result
92.376
Roof surface area
Material to order101.614
Flat footprint area80
AI explanation
Formula
Roof surface area = footprint area ÷ cos(slope angle); material to order = surface area × (1 + wastage%)Worked example
10m × 8m footprint, 30° slope, 10% wastage
| Field | Value |
|---|---|
| Roof footprint length (m) | 10 |
| Roof footprint width (m) | 8 |
| Roof slope angle (degrees) | 30 |
| Wastage allowance (%) | 10 |
| Flat footprint area | 80 |
| Roof surface area | 92.38 |
| Material to order | 101.61 |
Assumptions
- Assumes a simple single-slope roof — a hipped or gabled roof with multiple slopes needs each slope's area calculated and summed separately (run this calculator once per slope).
Frequently asked questions
Why is the roof surface area larger than the footprint?
A sloped roof's actual surface is longer than its flat horizontal footprint — the steeper the slope, the bigger the difference.
What's a typical roof slope angle?
It varies by roof type and climate — anywhere from a nearly flat 5-10° to a steep 45°+. Check your roof design drawing for the exact angle, or use the Roof Pitch Calculator if you know the rise and run instead.
How do I handle a hipped or gabled roof with multiple slopes?
Calculate each slope's footprint and area separately (they may have different dimensions or angles), then add the results together.