Roof area · uniform pitch
Roof area · uniform pitch: use length, width, pitch rise per 12 horizontal units. Review the formula, worked example and calculation steps.
Inputs
Use the units shown—
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Formula & explanation
Roof area = plan area × √[1+(rise/12)²] × (1+waste/100)
Variables & units
- Length
- m · minimum 0, maximum 1000000000000
- Width
- m · minimum 0, maximum 1000000000000
- Pitch rise per 12 horizontal units
- rise/12 · minimum 0, maximum 48
- Waste allowance
- % · minimum 0, maximum 100
Worked example
A flat 5 m × 4 m plan with no allowance has area 20 m².
Assumptions
Uniform pitch over the entire rectangular projected footprint. Include eaves in the plan dimensions. Complex valleys, dormers and different pitches need separate areas.
Formula version 1.0.0. JavaScript floating-point arithmetic applies. Results display up to 6 decimal places; stored values retain available precision. Use the units shown.
Practice with an example
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