Roof Area Calculator
Estimate the sloping surface area of a simple pitched roof.
Estimated roof area
73.25m²
- Sloping length
- 3.66 m
Assumes a simple symmetrical two-slope roof and excludes hips, valleys, dormers and overhangs.
v1.0 · Reviewed September 2026
How this is worked out
The sloping length of one side is the half-span divided by the cosine of the pitch. The area is that length × building length × 2 for the two slopes.
Worked example
- Building length 10 m
- Half-span 3 m
- Pitch 35°
3 ÷ cos 35° = 3.66 m, then 10 × 3.66 × 2 = 73.25 m²
73.25 m²
Assumptions and limits
- Assumes a simple symmetrical roof with two equal slopes.
- Hips, valleys, dormers, overhangs and abutments are not included.