Method
For a symmetrical gable roof, slope factor = √(1 + (rise ÷ 12)²). Roof area = building length × building width × slope factor.
Example
A 12 m by 8 m building with a 6:12 gable pitch has about 107.33 m² of roof surface before waste or overhangs.
Limits
Check inputs and units. Important academic, financial or professional decisions should be confirmed against an appropriate source.
Common questions
How do I calculate a sloped roof surface area?
Multiply the building plan area by the slope factor derived from the roof rise per 12 units of run.
Does the roof measurement include overhangs and waste?
No. Add overhang dimensions before calculating and apply a separate material-waste allowance appropriate to the project.
What does the roof area calculator calculate?
Estimate sloped gable roof area from building dimensions and roof pitch.
Does this roof area calculator show its method?
Yes. The result includes the central formula or working needed to check the answer.
Are my values uploaded?
No. The calculation runs in this browser and does not require an account.