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Calculators/Construction
Roofing Calculator
Calculate roofing material needs in squares, square feet, and shingle bundles. Accounts for roof pitch using the standard rise/run method. Includes waste percentage.
ft
ft
4/12
Pitch factor: 1.054 (multiplier over flat)
%
Material Breakdown
Area Per Side (before waste)843 sq ft
Total Area (both sides, +waste)1940 sq ft
Roofing Squares19.40
Shingle Bundles (÷3)59 bundles
Roofing Material Needed
19.40 squares
Total Sq Ft
1940 sq ft
Shingle Bundles
59 bundles
How to Use This Calculator
1
Measure ridge length and rafter span
Ridge length is the horizontal distance along the peak of the roof. Width per side (rafter span) is the horizontal distance from the ridge to the eave — NOT the actual rafter length. Measure horizontally, not along the slope. For a gable roof, there are two equal sides.
2
Understanding roof pitch
Pitch is expressed as rise over run (rise per 12 inches of horizontal run). A 4/12 pitch rises 4 inches for every 12 inches horizontally. A 6/12 pitch rises 6 inches. Steeper pitch = more actual surface area = more material needed. The pitch factor corrects for this: a 6/12 pitch has 11.8% more surface area than a flat roof.
3
Squares vs bundles
A roofing 'square' = 100 square feet of coverage. Standard shingles come in 3 bundles per square (33.3 sq ft/bundle). Premium or oversized shingles may use 4 bundles per square. Check your shingle packaging. Always order 15–20% extra for waste, valleys, hips, and ridges.
Real-World Examples
Standard Ranch Roof
Ridge Length
40 ft
Width Per Side
20 ft
Pitch
4/12
Waste
15%
Result19.4 squares — 59 bundles
Pitch factor: 1.054. Base area: 2 sides × 40 × 20 × 1.054 = 1,686 sq ft + 15% waste.
Steeper Cape Cod Roof
Ridge Length
35 ft
Width Per Side
18 ft
Pitch
8/12
Waste
20%
Result20.2 squares — 61 bundles
8/12 pitch factor: 1.202 — adds 20% more surface area vs flat, requiring significantly more materials.
Frequently Asked Questions
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