Roofing Calculator

The address lookup uses Google's aerial and 3D roof data to estimate the true roof surface area and average pitch. It's accurate enough for a fast quote on most existing homes, but it isn't a substitute for an on-site or drone measurement on complex roofs. Always verify before ordering materials. New construction, heavy tree cover, and rural buildings may have no data — in that case, measure by hand.

A roofing square is 100 square feet of roof surface. Roofers price and order materials by the square. A 2,000 sq ft roof is 20 squares. Shingles are sold in bundles, with three bundles covering one square of standard architectural shingles.

Your house's base area is its flat footprint. The roof sits on a slope, so its actual surface is larger. We multiply the footprint by a pitch multiplier — √(rise² + 144) ⁄ 12 — plus the eave overhang. A 6/12 roof has about 12% more surface than its footprint; a 12/12 roof has about 41% more.

Most roofers add 10% for waste on a simple gable roof and 15% or more on cut-up roofs with lots of hips, valleys, and dormers. The default here is 10%. Bump it up for complex roofs or premium shingles where off-cuts can't be reused.

Most residential roofs fall between 4/12 and 9/12. If you can safely measure, hold a level 12 inches out from the roof and measure the vertical drop at the end — that drop in inches is your rise. The address lookup estimates pitch automatically where data exists.

Yes. When you measure from an address, Google returns the pitch of every roof face. Any face flatter than 2/12 is treated as low-slope and split out automatically — those sections get a membrane system (torch-on, modified bitumen, TPO, or EPDM), not shingles. The tool shows the flat area separately and estimates membrane rolls for it, while the sloped faces are estimated as shingles. You can also enter a flat area by hand if you're not using the address lookup.

Flip on 'Replace roof decking (re-sheet)' and the tool adds 4×8 ft sheathing panels for the whole roof. Important: no satellite or aerial tool can tell whether your plywood or OSB is rotten or sagging — deck condition is only visible once the old roofing is torn off. Treat re-sheeting as a contingency you confirm on site, not something measured remotely.

Ice and water shield is a peel-and-stick membrane applied along eaves and in valleys, and it's required by code in cold climates (including most of Canada and the northern US). The tool estimates the linear feet of eaves and valleys from the roof's footprint and converts that to rolls (a 36-inch roll covers about 66 linear feet). It's on by default — turn it off in warm climates, and adjust the linear footage for your actual eave and valley runs.

No. This is a fast field estimate covering roof area, squares, shingle bundles, underlayment, flat-roof membrane, ice and water shield, and optional decking. It doesn't size drip edge, starter strip, ridge cap, step flashing, or labor, because those depend on the roof's perimeter and detailing. Use it to scope a job, then build a full estimate from there.

Yes — completely free, no signup. If you want to send the estimate to a customer as a branded quote or invoice and get paid online, you can do that free with Invoicer.ai.