About this site

What the site is

Roofings Calculator is an independent website with 60 calculators covering the whole of a pitched or flat roof: asphalt shingles and the starter, cap, nails, underlayment, ice barrier, drip edge and flashing that go with them; roof pitch, area, rafters, hips, trusses and ladders; metal, tile, slate, cedar and membrane roofs; gutters and downspouts; attic ventilation and insulation; and what a roof costs to replace, repair, tear off and plan for. A set of guides explains the inputs those calculators depend on.

Roofing is ordered in squares, bundles, rolls and 10-foot sticks, and priced in squares, and most of the confusion in a roofing quote comes from not knowing how those numbers were reached. Every calculator here starts from measurements you can take from the ground, uses a labelled default for anything you do not know, and shows the arithmetic it did with it.

How the calculators are built

Each calculator is a small program with an explicit formula, listed on its page under "How we calculate this". The same code produces the example result shown when the page loads, the result you get when you press Calculate, and the worked examples in the text, so the three can never disagree. Before a calculator is published it is run against a set of test cases with known answers, including unit conversions, and it is published only when they all pass.

The defaults come from public sources: manufacturers' published coverage and installation data and the Asphalt Roofing Manufacturers Association for shingles; the International Residential Code for underlayment, ice barriers, flashing, ventilation and overlays; the Cedar Shake and Shingle Bureau and the National Slate Association for cedar and slate; the SMACNA sheet-metal method and NOAA rainfall data for gutters; Energy Star for insulation levels; OSHA for ladders and fall protection; and dated 2025 cost surveys for prices. Each calculator's assumption table says which figure was used and when it was last checked; the methodology page lists the sources in one place.

Who writes it

The site is written and maintained by its publisher, with AI writing tools used to draft and to check text, and with every number, formula and claim reviewed by a person before it goes up. We say this plainly because readers deserve to know how what they read was made. The editorial policy sets out the rules we follow, how corrections are handled, and how advertising is kept separate from content.

We are not roofers, engineers or inspectors, and the site does not pretend otherwise. The calculators measure and count; they do not certify that a structure can carry a roof, that a roof is safe to walk on, or that a quote is fair. See the disclaimer.

What the site does not do

• It does not ask you to sign up, and it keeps nothing you type into a calculator. The arithmetic runs in your browser.
• It does not take money from roofing manufacturers, suppliers or contractors, it does not rank brands, and it does not recommend specific products.
• It never tells anyone to climb onto a roof to take a measurement, and it gives no procedures for asbestos or structural work.
• It does not claim precision it does not have. Where a figure is an estimate, the page says so and says how wide the range is.

Contact

Found a result that looks wrong, a source that has changed, or a calculator you wish existed? Use the contact form or write to contact@roofingscalculator.com. Reports of errors are checked first and answered. Publishers who want a calculator on their own site can use the embed codes.