Roofing Calculator — squares, bundles and pitch area
Roofing squares and shingle bundles from a building footprint, with the pitch multiplier that makes a roof larger than the house beneath it.
Roofing Calculator — squares, bundles and pitch area
The number people get wrong is the area. A roof is bigger than the house it sits on, and by exactly how much depends on the pitch. Everything else follows from that one multiplier.
| Footprint incl. overhang | — |
|---|---|
| Pitch multiplier | — |
| Actual roof area | — |
| With waste | — |
| Squares | — |
| Shingle bundles | — |
| Underlayment rolls | — |
A roofing square is 100 ft² of roof surface — that is a definition,
not an estimate. The pitch multiplier is √(rise² + 12²) ÷ 12: a 6:12 roof is
about 1.118 times its footprint, a 12:12 roof about 1.414. Measuring the house and forgetting the
multiplier is how orders come in short.
Bundles per square and underlayment coverage vary by product — three bundles per square is
ordinary for architectural asphalt shingles but is not universal, so check the wrapper. Waste
percentages here are for the field only; hip, ridge and starter courses are separate items and are not
counted above. This estimates material, not the tear-off, decking, flashing or labour.