Disclaimer

Estimates, not quotes

The calculators work out figures from the values you enter plus the labelled default assumptions on each page. They are arithmetic, not predictions. Treat every result as a well-explained estimate and check it against your own measurements, the product’s label and installation instructions, and a contractor’s written quote before acting on it.

Not structural, safety, legal or insurance advice

Roofing touches the structure of a building, the safety of the people working on it, the building code and, often, an insurance claim. The calculators measure and count; they are not a substitute for the professionals and documents that govern those questions:

• Structure. Rafter and hip lengths, truss counts and roof weights are geometry and arithmetic. Whether a rafter, truss or deck can carry a roof, especially a heavier one such as tile or slate, depends on spans, spacing, lumber grade and snow load, and must be checked against the code’s span tables, the truss manufacturer’s design or by a structural engineer.
• Safety. Nothing on this site is an instruction to go onto a roof. Ladder and fall-protection figures follow OSHA rules but do not make a roof safe to work on; steep, high, wet or damaged roofs are work for equipped professionals.
• Code and permits. The site cites the International Residential Code as a reference. Your jurisdiction’s adopted code, its amendments (including ice-barrier and wind maps and solar setbacks) and its permit requirements govern.
• Hazardous materials. Roofing and insulation made before about 1980, and vermiculite insulation, may contain asbestos. The site points to the US Environmental Protection Agency and gives no handling or removal procedures.
• Insurance. The site gives no advice on insurance claims beyond reading your policy and talking to your insurer.

Specific limits of this site’s calculators

Quantities assume rectangular roof planes of one pitch unless a calculator says otherwise, regular hips and valleys at 45 degrees in plan, and the coverage, laps and exposures stated in each assumption table. A product’s own data sheet and installation instructions govern over our defaults, and manufacturers’ warranties depend on following them.

Cost calculators use national survey ranges from 2025 with simple factors for pitch, height and region. Real prices depend on local labor rates, the contractor, the season, the roof’s complexity and what is found when the old roof comes off; a calculator range does not predict any particular quote.

Life expectancies, replacement windows and maintenance figures are planning ranges from industry surveys, not inspections or predictions about your roof. Rainfall intensities, insulation levels and ventilation requirements should be taken from the official source for your location rather than from our defaults.

Sources and updates

Default figures come from public sources named on each calculator’s assumption table and on the methodology page, with the date they were last checked. We update them when sources change and at least once a year, but a default may be out of date on the day you use it. Your own figures are always better than ours.

Advertising

Advertisements on the site are served by Google AdSense and are labelled as advertisements. We do not choose or endorse the products advertised, and an advertisement’s appearance next to a calculator does not mean the calculator was built with that product in mind.

Errors

If a calculator or a guide is wrong, we want to know. Write to contact@roofingscalculator.com or use the contact form; error reports are checked first. Our editorial policy explains how corrections are made and recorded.