Methodology
Where every number comes from
If we can't show you the source, we don't show you the number. This page documents exactly how an estimate is built.
Labor — government wage data
Trade labor rates are derived from published U.S. Bureau of Labor Statistics occupational wage data, by state, adjusted for crew productivity (squares installed per day) and job complexity. Steep pitch and multi-story access add documented labor multipliers.
Materials — tracked supplier prices
Material costs are sampled from major supplier pricing and refreshed monthly, with a 10% waste factor applied to all quantity math. The last-updated date appears on every calculator.
Measurement — your inputs
Roof geometry comes from measurements you enter: footprint, pitch, shape and section count. We apply the pitch multiplier — the true secant of the roof angle — to convert your footprint into actual roof surface. You control every input, and you can see exactly how each one changes the result.
Real prices — verified submissions
Homeowner-reported prices and public building-permit records are reviewed before publication and labeled by source. We never publish fabricated entries or invented "national averages."
The math, in the open
| Step | Formula |
|---|---|
| Roof area | footprint × pitch multiplier × overhang factor |
| Squares | roof area ÷ 100 |
| Pitch multiplier | sec(angle) — e.g. 6/12 = 1.118, 12/12 = 1.414 |
| Materials | squares × material rate × 1.10 (waste) |
| Labor | squares × state rate × complexity × steepness |
| Add-ons | tear-off, underlayment, ice shield, ventilation, dumpster |
| Total | materials + labor + add-ons + permit |
Estimates are planning ranges, not quotes. Final pricing always depends on an on-site assessment by a licensed contractor. Always compare multiple written bids.