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Roofing Calculator

Estimate roof surface area and roofing squares from building footprint, roof pitch and waste.

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Free tool

Building footprint length.

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Building footprint width.

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Pitch expressed as rise per 12 inches of run.

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Cutting and roof-layout allowance.

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Formula

Roof area = footprint area × √(1 + (rise ÷ 12)^2). Roofing squares = roof area ÷ 100 × (1 + waste%).

Roof area = footprint area × √(1 + (rise ÷ 12)^2). Roofing squares = roof area ÷ 100 × (1 + waste%).

How it works

1

Enter the building footprint.

2

Enter roof rise per 12 inches of run.

3

Review roof area and roofing squares.

Important notes

This simplified model assumes a consistent pitch over the footprint; dormers, hips and valleys can increase material needs.