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Roof area and pitch

Calculate roof area from horizontal dimensions, pitch and overhangs, with optional purchase costs.

Estimated purchase cost

Net prices. Optional VAT applies to materials, delivery and labour. Set VAT to 0 for already inclusive prices.

Roof area

Enter the measurements, then calculate.

Assumptions

Rectangular horizontal projection, equal pitch on all slopes and horizontal overhangs on both sides. Flat means 0°. No dormers, valleys, openings, cut layout, structural or product suitability checks.

A = (L + 2 × o₁) × (W + 2 × o₂) × √(1 + tan²(θ))

Pack coverage ·Assumptions

From measurements to a purchase

Worked examples use hypothetical product data, prices and allowances. Replace them with your measurements and the current supplier documents.

Measure the horizontal projection and add each overhang only once. L and W are the base dimensions; o₁ and o₂ are horizontal overhangs on both corresponding sides. Use degrees, percentage or rise/run as selected: 30° is about 57.735%, not 30%. Do not apply the slope factor to an area already measured along the roof.

With a 10 × 8 m projection including overhangs and a common 30° pitch, the slope area is about 92.376 m². An illustrative 10% allowance gives 101.614 m². Effective coverage of 10 m² per package requires 11 packages, covering 110 m². Check laps already included in coverage, cuts and accessories separately; when transferring the planned area, use 0% additional allowance.