calcmyroof.com

Methodology

This page explains where every number on calcmyroof.com comes from, how the cost ranges are built, how often they are checked, and what they are not. If a figure on this site cannot be traced back to something listed here, that is a mistake and we want to hear about it.

Cost figures are reviewed periodically. Last reviewed: September 8, 2026.

All cost figures on this site are national estimates, not quotes. They are researched from the public sources listed below. Nobody involved in this site installs roofs, and we do not claim any field experience. What we add is collecting public data in one place, showing the arithmetic, and keeping it current.

The calculators are plain arithmetic

None of the calculators use pricing data, a database or anything hidden. They take the measurements you type in and apply formulas that are printed on the page next to every result, so you can check the working or repeat it by hand.

  • Roof Pitch Calculator: pitch = 12 × rise ÷ run; angle = atan(rise ÷ run); multiplier = √(rise² + run²) ÷ run; slope % = rise ÷ run × 100.
  • Roofing Square Calculator: footprint = length × width; roof area = footprint × pitch multiplier; squares = area ÷ 100; squares with waste = squares × (1 + waste %); bundles = squares with waste × 3, rounded up.

The only assumptions built into a calculator are stated on its page. The main one is 3 bundles per square, which is the packaging convention for standard three-tab and most architectural asphalt shingles. Heavier designer shingles can be 4 or 5 bundles per square, and the calculator page says so.

Where the cost figures come from

Cost pages on this site quote a low, mid and high figure per roofing square, and a total for typical roof sizes. Those ranges are built from four kinds of public source. Every link below was checked and working on the review date above.

1. Manufacturer product data

Used for product lines, coverage per bundle, bundles per square, warranty tiers and installation requirements. Manufacturers do not publish public price lists, so these pages are not used for prices.

2. Retail material pricing

Per-bundle and per-roll prices for shingles, underlayment, starter strip, ridge cap, drip edge and nails are read from the public online listings of Home Depot and Lowe’s at each review, using their national listing price rather than any single store. We record the price per bundle and convert it to a price per square at 3 bundles per square. We do not link to individual product listings because retailer URLs and prices change too often for a link to stay accurate; anyone can repeat the check by searching either retailer’s site for the product names on the manufacturer pages above.

3. Federal wage statistics

Used to check the labor share of published job costs and to understand how labor differs between states. Installed labor per square is not the same as a roofer’s wage: a contractor’s price includes crew size, insurance, equipment, overhead and margin. We use wage data as a sanity check on survey figures, not to build labor cost from scratch.

4. Published contractor cost surveys

These are the main input for the total-job ranges. Each survey uses its own roof size, material and method, so we never average them blindly. We note what each one measured, convert to a per-square figure where the survey states the roof size, and cross-check the material share against the retail pricing above.

5. Industry technical references

Used for installation conventions such as minimum pitch for shingles, underlayment requirements and waste allowances, not for prices.

How a cost range is built

  1. Material per square. Retail price per bundle × 3, plus an allowance for underlayment, starter, ridge cap, drip edge and fasteners priced from the same retailers. This gives a low and high material figure per square depending on shingle grade.
  2. Installed cost per square. Taken from the published surveys, converted to per-square using the roof size each survey states. The spread between surveys becomes the low and high end of the range.
  3. Cross-check. The material figure from step 1 should sit at roughly 30 to 50 percent of the installed figure from step 2 for asphalt shingles. If it does not, one of the inputs is wrong and we re-check before publishing.
  4. Rounding. Per-square figures are rounded to the nearest $5 and totals to the nearest $100. We publish ranges, not single numbers, because a single number would imply a precision the data does not have.

Every cost page lists the sources used for that page and carries its own “Last updated” date. Where a page gives a figure for a particular state, the page states how it was derived from the national range.

How often figures are updated

  • Cost figures are reviewed periodically. Each cost page shows the date it was last reviewed.
  • A review is also triggered when the Producer Price Index for building materials moves noticeably, or when one of the surveys above publishes a new edition.
  • At each review, every source link on this page is re-checked. Sources that have gone offline or behind a paywall are removed rather than left as dead links.
  • Calculator formulas do not need updating. If an assumption such as bundles per square changes, the change is noted on the calculator page.

What the figures are not

  • Not a quote. Your price depends on your roof, your region, the season, the contractor and what they find when they tear off the old roof. Get at least three written estimates.
  • Not local. Unless a page says otherwise, figures are national. Labor and material costs in high-cost metro areas can sit well above the top of a national range.
  • Not expert opinion. Nobody here has installed a roof. The figures are researched from the sources above and the arithmetic is shown. Where a claim needs field judgment, such as whether a roof can be overlaid rather than torn off, the page says to ask a contractor.
  • Not influenced by advertisers. Quote request forms on the calculator pages connect homeowners to third-party contractor networks. Those partners do not supply, review or influence any figure published here.

Corrections

If you find a figure that does not match its source, a source that has changed, or a calculator result that looks wrong, use the contact page and include the page and the number. Corrections are made when a better public source exists, and the page’s review date is updated when they are.