Roofing Calculator — Full Material Estimator
Get a complete roofing material list — squares of shingles, underlayment rolls, ridge cap bundles, starter strip and drip edge — from your building footprint, pitch and roof type.
ft
ft
/12
ft
ft
%
Squares of roofing material to order (including waste)
- 1
Pitch factor
√(1 + (6 ÷ 12)²) = 1.118Converts the flat building footprint to the true sloped roof surface area. - 2
Footprint area
50 × 30 = 1,500 - 3
Sloped roof area
1,500 × 1.118 = 1,677.1 - 4
Roofing squares (÷ 100)
1,677.1 ÷ 100 = 16.77 - 5
Squares to order (+ waste, rounded up)
⌈16.77 × 1.1 × 10⌉ ÷ 10 = 18.5
How does this calculator work?
True roof area = footprint × pitch factor (√(1+(rise/12)²)). Divide by 100 for squares, add 10–15% waste, and round up. Underlayment: squares × 100 ÷ 400 rolls. Ridge cap: total ridge+hip linear footage ÷ 25 per bundle. Drip edge: eave plus rake perimeter in linear feet.
Formula
How this is calculated
The sloped roof surface is always larger than the flat building footprint because of the pitch. The pitch factor sqrt(1 + (rise/12)²) converts the footprint area to sloped area. Dividing by 100 gives roofing squares — the standard unit for ordering shingles (one square = 100 sq ft of coverage). A waste allowance (typically 10% for simple gables, 15% for roofs with hips) accounts for cuts at ridges, rakes, valleys and for breakage.
Underlayment (felt paper 15# or synthetic) protects the deck while shingles are installed. A standard 15# felt roll covers about 400 sq ft; synthetic rolls vary (check the packaging). Ridge cap shingles are sold in bundles covering approximately 25 linear feet of ridge or hip; the calculator adjusts hip rafter lengths for slope. Starter strip bundles cover about 105 linear ft of eave.
Drip edge runs along all eave and rake edges to channel water away from the fascia; the total is the sum of eave lengths plus the pitch-adjusted rake lengths on each side. All quantities are rounded up to whole units as you would order them. Actual waste depends on the roofer's technique and roof complexity — for complex roofs with dormers, valleys, or skylights, increase the waste percentage to 15–20%.
Frequently asked questions
One roofing square equals 100 square feet of finished roof surface. Standard 3-tab asphalt shingles require three bundles per square; architectural (laminate) shingles are typically 2–3 bundles per square depending on weight — check the product packaging.
Most building codes require an underlayment layer (felt or synthetic) beneath asphalt shingles. It acts as a secondary moisture barrier. 15# felt covers about 400 sq ft per roll; lighter synthetic products can cover 1,000–1,500 sq ft per roll — adjust the roll estimate if using synthetic.
Ridge cap shingles are pre-cut shingles (or cut from regular shingles) that wrap the peak of the ridge and hip rafters, shedding water from the very top. One bundle covers about 25 linear feet of ridge. Enter the full length of all ridges and hips so the calculator includes the right amount.
Also known as
TG we-Calculate Editorial Team. (2026). Roofing Calculator — Full Material Estimator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/roofing-calculator
TG we-Calculate Editorial Team. "Roofing Calculator — Full Material Estimator." TG we-Calculate. 2026. https://we-calculate.com/calculator/roofing-calculator.
TG we-Calculate Editorial Team, "Roofing Calculator — Full Material Estimator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/roofing-calculator
@misc{wecalculate_roofing_calculator, title = {Roofing Calculator — Full Material Estimator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/roofing-calculator}}, year = {2026}, note = {TG we-Calculate} }
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