The calculator estimates the sloped surface and rounds material packs up to a whole pack.
Home & Construction calculator
Roofing Calculator
Use the plan dimensions, roof pitch and overhang to create a first material-order estimate for a simple rectangular roof.
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No account. Formula and assumptions are shown below.
Calculator inputs
Roofing materials details
Formula & disclaimer
Roof Area = (Length + 2 Γ Overhang) Γ (Width + 2 Γ Overhang) Γ· cos(Pitch); Order Area = Roof Area Γ (1 + Waste)
View assumptionsFormula reviewCalcs at Hand Editorial TeamVerified 31 August 2026 Β· automated checks included
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Projection
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Formula & details
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How to read this result
Three useful checks, kept deliberately short.
A 12 m Γ 8 m building, 25Β° pitch, 0.5 m overhang and 10% waste: Expand the roof plan for overhang Β· Apply the pitch multiplier Β· Add the waste allowance.
Valleys, hips, dormers, complex overlaps, flashing and product-specific lap requirements need a detailed take-off.
Formula and assumptions
Roof Area = (Length + 2 Γ Overhang) Γ (Width + 2 Γ Overhang) Γ· cos(Pitch); Order Area = Roof Area Γ (1 + Waste)The calculation models a simple rectangular roof with a uniform pitch.
Keep in mind: Confirm roof geometry, structural requirements, safe installation and product coverage with a roofing professional.
Produced byCalcs at Hand Editorial Team
Last formula check31 August 2026
Review methodKnown examples + boundary cases
Editorial and correction policy β