Roofing Calculator
Estimate roofing materials for gable and hip roofs. Calculates squares, shingle bundles, felt rolls, and nails. Includes pitch multipliers and waste factors.
Roofing
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Est. Material Cost
Enter price per square for estimate
Materials List
{"squares":15,"bundles":45,"feltRolls":4,"nailsLbs":30,"ridgeLength":"42"}
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15
Squares Needed
45
Shingle Bundles
Pitch Multiplier
Shopping List
Home Depot Ready
Take this list to Home Depot or your local supplier. Standard architectural shingles come in 3-bundle squares. Felt paper comes in rolls covering ~400 sq ft each.
The Formula
Roofing material quantities are calculated from the building footprint adjusted for roof pitch, overhang, waste, and roof type.
Variable Definitions
Pitch Multiplier
Factor that accounts for the increased surface area of a sloped roof vs flat.
Squares
A roofing square = 100 sq ft. Industry standard for quoting material.
How to Use This Calculator
- 1
Enter building length and width.
- 2
Select roof pitch from the dropdown.
- 3
Choose roof type (gable or hip).
- 4
Add overhang and waste factor.
- 5
Review squares, bundles, and materials.
Roof pitch = rise / run, measured in inches per 12 inches of horizontal run
Understanding the Concept
Roofing is measured in "squares" where 1 square = 100 square feet. The pitch multiplier accounts for the extra surface area created by the slope. Hip roofs require ~5% more material than gable roofs due to complex cuts. Always add a waste factor of 10-15% depending on roof complexity. Practical example: a house measuring 40 feet by 30 feet with a 6/12 pitch and 1 foot overhang on all sides. The effective footprint is (40 + 2) × (30 + 2) = 42 × 32 = 1,344 sq ft. Using the pitch multiplier of 1.118 for 6/12, the roof surface area is 1,344 × 1.118 = 1,503 sq ft. With 10% waste on a gable roof: 1,503 × 1.10 = 1,653 sq ft, which is 16.53 squares, rounded up to 17 squares requiring 51 bundles of shingles. Edge cases: for roofs with multiple valleys, dormers, or chimneys, waste can reach 20% because of complex flashing and cutting around obstructions. For flat roofs (0/12 pitch), the pitch multiplier is 1.000 but additional material is needed for tapered insulation to ensure proper drainage — at least 1/4 inch per foot slope. For metal roofing, the square calculation differs because panels are ordered by linear foot with specific coverage widths, and ridge caps, drip edges, and flashings must be accounted for separately. In high-wind areas, consider upgraded underlayment and additional fasteners per square.
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