Roofing Shingles & Squares Calculator
Estimate the roofing squares and shingle bundles you need from your roof footprint, pitch, and waste allowance.
ft
ft
/12
%
At 3 bundles per square, rounded up
- 1
Pitch factor
√(1 + (6 ÷ 12)²) = 1.118 - 2
Sloped roof area
40 × 30 × 1.118 = 1,341.6 - 3
Roofing squares
1,341.6 ÷ 100 = 13.42 - 4
Bundles to order
⌈13.42 × 3 × 1.1⌉ = 45Three bundles per square, plus waste allowance, rounded up to whole bundles.
How does this calculator work?
Multiply your roof footprint (length × width) by the pitch factor sqrt(1 + (rise/12)^2) to get true roof area, divide by 100 for squares, then multiply squares by 3 bundles and add a waste allowance (about 10%) and round up to find how many shingle bundles to buy.
Formula
How this is calculated
The footprint length and width give the flat area the roof covers (length × width). Because a sloped roof is larger than its flat footprint, the pitch converts that footprint into true roof area. Pitch is entered as rise per 12 inches of run, so a "6/12" roof rises 6 inches for every 12 inches horizontal. The pitch (slope) factor is sqrt(1 + (rise/12)^2); multiplying the footprint by this factor yields the actual sloped roof area in square feet.
Roofers measure coverage in "squares," where one square equals 100 square feet (about 9.29 m²). Dividing the roof area by 100 gives the number of squares. Asphalt shingles are typically sold three bundles per square, so multiplying squares by 3 gives the base bundle count.
Real jobs need extra material for starter courses, ridge caps, hip and valley cuts, and breakage, so a waste allowance (commonly 10%) is added before rounding up to whole bundles. Results assume a simple gable-style footprint and three bundles per square; complex roofs with many hips, valleys, or dormers may need a higher waste percentage. Inputs use feet for footprint and inches of rise per 12 for pitch; enter 0 rise for a flat roof (pitch factor 1).
Frequently asked questions
Standard three-tab and most architectural asphalt shingles come three bundles to a square (100 sq ft of coverage). This calculator uses three bundles per square, then adds your waste allowance and rounds up.
A roofing square is 100 square feet of finished roof surface (roughly 9.29 square meters). Squares are the standard unit roofers use to price and order material.
Steeper pitches increase the actual sloped area above the flat footprint. A 6/12 pitch adds about 12% area, while a 12/12 pitch adds about 41%, so steeper roofs need proportionally more shingles.
Also known as
TG we-Calculate Editorial Team. (2026). Roofing Shingles & Squares Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/roofing-shingles-calculator
TG we-Calculate Editorial Team. "Roofing Shingles & Squares Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/roofing-shingles-calculator.
TG we-Calculate Editorial Team, "Roofing Shingles & Squares Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/roofing-shingles-calculator
@misc{wecalculate_roofing_shingles_calculator, title = {Roofing Shingles & Squares Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/roofing-shingles-calculator}}, year = {2026}, note = {TG we-Calculate} }
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