Quick Roof Area Calculator
Enter your house footprint and roof type to get the roof surface area instantly.
Your Roof
Result
Add 10–15% when ordering roofing materials to cover waste and cuts.
How to calculate roof area
The formula
Roof area = Footprint area × pitch factor. The pitch factor accounts for the slope — a steeper roof covers more surface than its floor footprint.
Pitch factors
Flat: factor = 1.0. 15°: 1.035. 30°: 1.155. 45°: 1.414. The steeper the pitch, the larger the factor.
Gable vs hip roof
A gable roof has two sloping sides and two flat triangular ends (gables). A hip roof has four sloping sides — all edges slope down to the eaves. Hip roofs have slightly more surface area than gable roofs of the same footprint.
What about overhangs?
The eave overhang extends beyond the wall face and adds to the roofing area. A typical overhang is 200–400 mm per side.