Roof Area Calculator
A sloped roof covers more ground than the walls below it, because it is longer than its footprint. This works out the actual surface area from the footprint and the pitch.
- Free
- Works offline after your first visit
- Saves on this device
- No sign-up
- Updated
How it works
The slope adds length. For a pitch written as the rise in inches for every 12 inches across, multiply the footprint by the square root of 144 plus the rise squared, divided by 12. A rise of 6 adds about 12 percent.
Roofers count in squares, where one square is 100 square feet. Divide the roof area by 100 to get squares, and add extra for overhangs and waste when you order.
Worked example
A house with a footprint of 1,500 ft², under a roof that rises 6 inches for every 12 across, has about 1,677 ft² of roof, or 16.8 squares.
Questions
What is pitch?
Pitch is how steeply a roof rises. It is often written as a rise in inches for every 12 inches across, such as 6 in 12.
Does this include overhangs?
No. It uses the footprint only. Add the area of any overhangs, then allow extra for waste and cut-offs.
Why are squares used?
Roofing is sold and counted in squares, one square being 100 square feet. Divide the area to see how many squares your supplier will need.
More like this
- Roof Truss CalculatorHow many trusses fit a roof at a set spacing.
- Area Rug Size CalculatorRug size that leaves an even gap at each wall.
- Roof Pitch CalculatorRoof slope as a ratio, angle and area factor.
- Concrete CalculatorCubic yards or metres of concrete, and the cost.
- Concrete Bag CalculatorBags of 40, 60 and 80 lb for a volume.
- Concrete Slab CalculatorYards and bags for a slab.