Roofing Calculators

Working with roofing quantities

Roofing quantities all start from the same place: the building footprint and the pitch. The pitch multiplier converts flat area into actual sloped area, so you never need to get on the roof to estimate it. A 6/12 roof has 11.8% more surface than the ground it covers; a 12/12 roof has 41.4% more.

Worth knowing: Allow 10% waste on a simple gable and 15% where there are valleys, hips or dormers. Every valley means cutting shingles at an angle, and those offcuts cannot be reused.

These 10 calculators cover about 40,980 searches a month between them. Every one prints the formula it uses and a worked example, so you can check the result by hand before you order.