Roofing Calculator
Calculate total roof area, roofing squares, shingles, and underlayment for a gable roof.
Formula
Roof area = footprint × pitch multiplier; multiplier = √(1 + (pitch/12)²); Squares = area / 100
- Pitch multiplier converts plan area to actual rafter surface area.
- 6:12 pitch multiplier = √(1.25) = 1.118. 12:12 = √2 = 1.414.
- 3 bundles per square (standard shingles).
50 ft × 30 ft building, 6:12 pitch
Inputs
- Building Length: 50 ft
- Building Width: 30 ft
- Roof Pitch (rise:12): 6 in/ft
Footprint = 1500 sq ft × 1.118 = 1677 sq ft. 16.77 squares × 1.10 = 18.4 squares. 56 bundles.
Frequently asked questions
What is a pitch multiplier?
Pitch multiplier converts horizontal (plan) area to the actual sloped roof area. A 6:12 pitch makes the roof 11.8% larger than the floor plan footprint.