Measuring the exterior
The roof and walls are both measured in squares — 100 square feet each — so a roof or siding job comes down to total area plus a waste allowance, with roofing adjusted for pitch (a steeper roof has more surface than its footprint). Gutters follow the length of your eaves, with downspouts spaced to drain the roof. Roof work is dangerous, so for steep or complex roofs, get a professional measurement.
Frequently asked questions
How is roofing measured?
By the 100 sq ft "square," about 3 bundles of shingles each. Steeper pitch adds area over the footprint, which the calculator handles.
How much siding or guttering?
Siding in 100 sq ft squares of wall area (minus openings) plus waste; gutters along the eaves with a downspout every 30–40 ft.