Roofing Calculator
Plane-by-plane footprint × pitch factor, an optional waste allowance, and whole purchase units from the coverage on your product's packaging — with pieces and cost when you supply them.
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Exterior & Roofing
Roofing estimates come down to three ideas: the horizontal footprint of each plane, the pitch that turns footprint into surface area, and the coverage your actual product delivers per unit. The tool and tips below handle the math — the measurements and the wrapper figures come from you.
Start with the calculator
What you can calculate
- Roof surface area for any number of planes — each with its own footprint and its own pitch, entered as rise over run.
- Pitch factors shown per plane, so you can check the math against a pitch chart or your plans.
- Purchase units — bundles, packs, squares, or rolls — rounded up to whole units from the coverage you enter. No product default is ever assumed.
- Total pieces when your product lists pieces per unit on the wrapper.
- Estimated cost from your own price per unit.
Measuring tips for roof planes
- Measure the horizontal footprint of each plane — the rectangle you would see on the house plans — not the sloped length. The pitch factor converts footprint to surface for you; applying it twice is the most common way to over-order.
- Pitch is rise over run in the same unit: 6 inches of rise over 12 inches of run is a 6/12 pitch. In metric, use the same ratio in centimetres — the factor is dimensionless.
- Include overhangs and dormer cheeks as their own planes when they will be covered; splitting a complex roof into more, smaller planes is more accurate than averaging.
- Measure from the ground, from plans, or from inside the attic where possible. Walking a roof for measurements carries real fall risk — that job belongs to a professional.
Guides for roofing projects
- How Much Roofing Do I Need? — the full manual method with a worked example.
- How Much Extra Material Should You Buy? — choosing a sensible waste percentage.
Related calculators
- Gravel Calculator — for ground-level outdoor coverage in the same project.
- All calculators — paint, flooring, drywall, tile, and more.
These tools estimate material quantities only. They do not assess structural condition, drainage, or code compliance, and they are not roofing or structural advice. For anything structural, or any work at height, consult a qualified roofing professional.