From footprint to squares
The calculator adds your eave overhang to the footprint, then multiplies by a pitch factor: the square root of 1 + (rise ÷ 12)². A 6/12 roof has a factor of about 1.118, an 8/12 about 1.202 and a 12/12 about 1.414. Divide the surface area by 100 to get squares, then add waste for cuts, hips and valleys.
Why waste matters
Hip roofs and cut-up roofs need more material than simple gables because of all the angled cuts. Estimates that use a low waste factor on a complex roof can understate material by several squares. Compare the waste factor in your estimate with the roof’s actual shape.
Steep and high charges
Estimating software typically adds labor charges for steep slopes and for roofs more than one story high. If your roof is 7/12 or steeper, look for those charges in the carrier’s estimate.
This tool gives a ballpark. Dormers, multiple pitches and complex geometry need real measurements or an aerial report.
Questions about this worksheet
How do I find my roof pitch?
A roofer, inspection report or aerial measurement report will list it. You can also measure the rise over a 12-inch level on the rafter or roof surface.
Why are my squares different from the carrier’s?
Differences in measurement, overhang, pitch or waste factor add up. Ask for the carrier’s measurement report and compare.
Does the cost estimate include tear-off?
Only if your price per square includes it. Use an installed price from a local contractor for the best rough figure.
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