Simple 6:12 roof
Typical roof square footage estimate.
1,377.42 sq ftRoofing arearoof square footage calculator
Roof Square Footage Calculator
Roof square footage is usually larger than the building footprint because pitch increases surface area.
Inputs
Results
Immediate estimateRoofing area1,377.42 sq ft13.77 roofing squares
Footprint1,120 sq ft
Pitch factor1.118
Base roof area1,252.2 sq ft
Estimated bundles42 bundles
Shopping list
- 42 bundles Asphalt shingles — Approximate; verify product coverage.
Diagram
Roof area
Building footprint is increased by pitch factor and waste.
- Footprint
- Pitch
- Roof surface
How this calculator works
Use building footprint, roof pitch, and waste allowance to estimate roof square footage and shingle bundles.
Formula
The engine multiplies footprint area by a pitch factor, adds waste, converts to roofing squares, and estimates bundles at three per square.
Footprint
building length × building widthPitch factor
sqrt(12² + rise²) ÷ 12Roof area
footprint × pitch factor + wasteAssumptions
- Roof shape: Simple gable or hip-style approximation based on footprint and pitch.
- Shingles: Bundle estimate assumes three bundles per roofing square.
Worked examples
Steep 14:12 roof
Shows steep-roof caution.
1,357.12 sq ftRoofing areaFAQ
Does this work for complex roofs?
It is best for simple early estimates. Valleys, dormers, cut-up roofs, and multiple slopes should be measured by roof plane.
What is a roofing square?
One roofing square equals 100 square feet of roof surface.
Sources and review
- Roof measurement and shingle planning, GAF. Accessed 2026-07-16.
Reviewed 2026-07-16. Planning estimates only; confirm project-specific requirements.