How the estimate works
Enter the approximate ground-plan area of the roofed section and select a pitch factor. The worksheet multiplies area by a roof-slope factor and converts square feet into roofing squares (100 square feet each).
It does not calculate roofing costs. It also does not account for dormers, hips, valleys, waste, overhangs or the measurement method a contractor will use.
Why this helps when reviewing bids
Ask each contractor whether the measured area is plan area or actual sloped surface, how much waste they included and why quantities differ. Numbers alone cannot identify a correct bid without plans or field measurements.
For complex roof shapes or structural concerns, use a professional survey or measured proposal. Do not climb the roof to get dimensions.
Keep quantities and prices separate
A roof that has the same nominal area as another may cost more to work on due to access, slope, tear-off, flashing, decking or labor. The worksheet is designed for informed questions, not an instant quote.
Roof surface estimator
Geometry-only estimate. No labor, material, permit, waste or price assumptions. Do not measure a roof by climbing it.
Sources and official guidance
Links checked for the November 2026 editorial draft. Verify rules again before beginning work.