Roofing squares calculator
Footprint area corrected for pitch, converted to squares, with waste. The correction is where roof quotes go wrong.
A footprint measurement is not a roof measurement. If you measure the building from the ground or off a satellite image, the actual roof surface is larger by a factor that depends on pitch, and pricing a steep roof off footprint area is not a small error.
Enter the footprint and the pitch. A 6/12 roof is roughly twelve percent larger than its footprint. A 12/12 is over forty percent larger.
Horizontal area covered by the roof, measured from the ground or off a satellite image.
A 6/12 roof rises 6 inches for every 12 horizontal.
7-10% on a simple gable. 15%+ on a cut-up roof with hips, valleys, and dormers.
What to order
| Pitch | Multiplier | Larger than footprint by |
|---|---|---|
| 3/12 | 1.031x | 3% |
| 4/12 | 1.054x | 5% |
| 6/12 | 1.118x | 12% |
| 8/12 | 1.202x | 20% |
| 10/12 | 1.302x | 30% |
| 12/12 | 1.414x | 41% |
This corrects the area only. Above roughly 7/12 the crew also slows down and starts needing staging, harnesses, and roof jacks, which is a labor multiplier on top of this and belongs on its own line. Folding the two together loses the labor half.
A roofing square is 100 square feet. Material quantities and most labor pricing in the trade run off it.
Pitch does a second thing this calculator does not cover. Above roughly 7/12 the crew slows down and starts needing staging, harnesses, and roof jacks. That is a labor multiplier on top of the area correction, and it needs to be its own line.
Seven to ten percent waste suits a simple gable. A cut-up roof with multiple hips, valleys, and dormers can run fifteen percent or more, and running short mid-install costs more than overbuying.
The reasoning behind these numbers is in How to estimate a roofing job.