Roofing Calculator

Estimate roof surface area from footprint dimensions and roof pitch.

Inputs

Building Length (m)

Building Width (m)

Roof Pitch (rise per 12)

E.g. 6 means a 6-in-12 pitch — 6 units of rise per 12 units of run.

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Roof Area (m²)

89.44

Footprint Area (m²)

80.00

Spark says

How it's calculated

Formula

Roof\ Area = Footprint \times \sqrt{1 + \left(\dfrac{Rise}{12}\right)^2}

Rise: — Roof rise per 12 units of horizontal run

What is the Roofing Calculator?

A pitched roof has more surface area than its flat footprint — this calculator applies the standard pitch multiplier to find the true roof surface area for material estimates.

How to use it

1 Enter the building's length and width.
2 Enter the roof pitch as rise per 12 units of run (a common roofing convention).

Worked examples

10m × 8m building, 6-in-12 pitch

Roof area is about 89.4 m².

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Frequently asked questions

What does a '6-in-12' pitch mean?

For every 12 units the roof runs horizontally, it rises 6 units vertically — a moderate slope. Steeper roofs have higher rise numbers.