Roofing Shingle Calculator
Estimate roofing squares and shingle bundles from roof footprint dimensions and pitch. Adjusts for roof slope and waste.
Assumptions
- Simple gable or hip roof approximated from rectangular footprint × pitch multiplier.
- One roofing square = 100 ft² of roof area.
- Three bundles per square is standard for many architectural shingles.
- Default waste is 10%; use 12–15% for complex roofs or starter strips.
- Does not include ridge cap, underlayment, or drip edge.
Footprint area = length × width. Roof area = footprint × pitch factor. Squares = roof area ÷ 100. Bundles = squares × bundles per square (typically 3). Waste is added to roof area before converting.40 × 30 ft footprint, 4/12 pitch
- Footprint = 1,200 ft². Pitch factor for 4/12 ≈ 1.054. Roof area ≈ 1,265 ft². Squares = 12.65 → 13 squares. At 3 bundles/square ≈ 39 bundles, plus waste.
How to measure
Measure the building footprint at the eaves from outside edge to outside edge. For pitch, use rise and run from the roof surface or a pitch gauge (e.g., 4 in rise per 12 in run = 4/12).
Common mistakes
- Using flat footprint area without pitch adjustment.
- Confusing bundles with squares (1 square ≠ 1 bundle).
- Forgetting waste for ridge, valley, and starter course cuts.
Frequently asked questions
What is a roofing square?
One square covers 100 ft² of roof area. Shingles are sold by the bundle; typically 3 bundles make one square.
How do I find pitch factor?
Enter rise and run (e.g., 4 and 12) and the calculator computes the multiplier, or enter the factor directly if you know it.
Hip roof vs gable?
Complex roofs need more waste. Use 12–15% and verify with a roof measurement app or contractor.
Architectural vs 3-tab bundles?
Bundles per square varies by product line — check your shingle packaging.