Roofing Calculator
Free roofing calculator: the real roof area from the building footprint and the pitch, in squares and shingle bundles or roof tiles, with waste included.
Footprint including the eaves
Also: Paint Calculator Β· Concrete Calculator Β· Square Footage Calculator
What it does
A sloped roof is larger than the floor it covers. Dividing the footprint (length × width, including the eaves) by the cosine of the pitch gives the real area for gable and hip roofs with the same pitch on every side. In the USA roofing is sold by the square (100 ft²), usually three bundles of shingles per square.
How to use it
- Enter the length and width of the building plus the eaves overhang.
- Enter the pitch as rise in 12, percent or degrees.
- Add the waste allowance and, for tiles, how many go in a square metre.
The arithmetic runs in your browser. Nothing you type is sent anywhere and nothing is stored, so you can use these with real numbers.
Frequently asked questions
How do I find the pitch of my roof?
Measure how much the roof rises over a horizontal distance: a rise of 6 inches over 12 inches is a 6/12 pitch, the same as 50% or about 26.6 degrees. Plans and the roof tile manufacturer usually give the pitch in percent.
How many roof tiles go in a square metre?
It depends on the model: roughly 16 for Roman or Portuguese clay tiles, 10 to 12 for concrete tiles and about 24 for small colonial tiles. Use the number on the manufacturer’s sheet.