Roof Area from Footprint and Pitch
Also known as roof area · shingle area · roofing square footage
Worked example: 1000 ft2 footprint at 9:12 → 1250 ft2 of roof (116.1288 m2) — press Try an example to run it live, then adjust anything.
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Roof Area from Footprint and Pitch explained
The same square root that stretches a rafter stretches the whole roof. Measure the building's footprint from the plan, multiply by , and you have the sloping area to be covered. A 1000 ft² footprint under a 9:12 roof is 1250 ft² of shingles, or 12.5 squares in roofing currency, since a "square" is 100 ft².
The multiplier is why steep roofs cost more than they look. It runs from 1.03 at 3:12 to 1.41 at 12:12, so going from a low slope to a 45° roof adds better than a third to the material before any of the labour premium for working on a pitch that steep. Add your hips, valleys and starter courses on top, usually 10 to 15 percent, and remember that this formula gives the plan-to-slope conversion only. Dormers, overhangs and rake extensions have to be measured and added separately.
Roof Area from Footprint and Pitch formula
- = Roof surface area (m²)
- = Footprint area (m²)
- = Pitch (rise per 12 of run) (in 12)
Missing one of these? Work it out first, then come back
- Roof surface area — Cone Total Surface Area, Torus Surface Area
- Footprint area — Area of a Circle, Area of a Triangle
- Pitch (rise per 12 of run) — Roof Pitch to Slope Angle, Common Rafter Length from Run and Pitch