Part of the square footage calculator set. Enter the house footprint and the roof pitch to get the sloped roof area, a waste allowance, and the roofing squares and shingle bundles to order. The table below shows how the same footprint changes area at every common pitch.
Updated September 2026 · Assumes one uniform pitch over the whole footprint.
Footprint, eave to eave, including overhang
Footprint, eave to eave, including overhang
Default 10%; use more for hips, valleys and dormers
The shingle wrapper states bundles per square
Installed price per 100 sq ft, if you have a quote
| Pitch | Angle | Multiplier | Roof area | Squares (incl. waste) |
|---|
A sloped roof covers more surface than the footprint underneath it, because the slope stretches every square foot of plan area along the pitch. The calculator multiplies the footprint by a pitch multiplier, adds a waste allowance, then divides by 100 to get roofing squares and by the bundles-per-square figure to get shingle bundles.
On the default 40 ft × 30 ft footprint at a 6/12 pitch: footprint = 1,200 sq ft, pitch multiplier = 1.1180, roof area = 1,341.64 sq ft. Adding 10% waste (134.16 sq ft) gives 1,475.8 sq ft to order, which is 14.76 squares — 15 squares rounded up — or 45 bundles at 3 bundles per square.
You can estimate a roof's area without climbing on it, using the house's footprint and its pitch:
A gable roof and a hip roof over the same footprint at the same pitch have the same surface area — the roof style does not change the area formula, because both shapes stretch the same plan area by the same pitch multiplier. What a hip roof (and any roof with valleys or dormers) changes is the waste: more hips, valleys and angled cuts mean more offcuts, so those roofs need a higher waste allowance than a simple gable, not a different area calculation.
The table above holds the footprint and waste allowance fixed and shows the roof area and squares at every common pitch, from flat (0/12) to steep (18/12). Pitch is expressed as rise over a 12-inch run, and the multiplier is √(1 + (rise ÷ 12)²) — it only depends on the ratio of rise to run, not on the size of the roof.
On the default footprint, a shallow 18.4° pitch (4/12) gives 1,264.91 sq ft of roof, while a steep 45.0° pitch (12/12) gives 1,697.06 sq ft — 432 sq ft more, about 34.2% higher, over the exact same footprint. Steeper roofs need more material and more labor for that reason, even when the house below is identical.
A roofing square is 100 square feet of roof surface, regardless of pitch. It is a unit for ordering material, not an area on the ground.
It depends on the shingle. Three bundles per square is a common packaging for three-tab and architectural shingles, but the wrapper states the actual figure for the product you are buying — use the bundles selector above to match it.
Yes. On the 40 ft × 30 ft footprint above, a 4/12 pitch gives 1,264.91 sq ft of roof, while a 12/12 pitch gives 1,697.06 sq ft — about 432 sq ft more, roughly 34.2% higher, from the same footprint.
That's your call, and it depends on the roof's complexity: a simple gable with few cuts needs less, while hips, valleys and dormers create more offcuts and need more. The calculator's default is only a starting point — check it against your roofer's estimate or the shingle manufacturer's guidance for your roof shape.