Roofing Calculator
Overall roofing material estimate from roof area, pitch and material type.
Result appears here
Fill in the fields and press Calculate.
Formula, calculation, assumptions and sources
Roof area = footprint × slope factor; slope factor = √(pitch² + 12²) ÷ 12
Squares = roof area ÷ 100; field bundles = squares × bundles per square
Ridge cap = ridge + hip length ÷ 25 ft; starter = eave + rake length ÷ 105 ft
Nails ≈ 2.5 lb per square
Run the calculation to see each step with your own numbers.
A 40 × 30 ft footprint, 6-in-12 roof, 3 bundles/square, 45 ft ridge, 140 ft eave+rake, synthetic underlayment (10 sq/roll), 10% waste.
Roof area = 1,200 × 1.118 = 1,342 ft² = 13.4 squares
Field bundles = 13.4 × 3 = 40.3 exact → 45 recommended (10% waste)
Underlayment = ⌈13.4 ÷ 10⌉ = 2 rolls; ridge cap = ⌈45 ÷ 25⌉ = 2; starter = ⌈140 ÷ 105⌉ = 2
Nails ≈ 13.4 × 2.5 = 33.5 lb (covers the actual roof — shingle waste is not nailed down)
- Simple gable/hip roof — footprint equals the horizontal projected roof area; add overhangs to the footprint if you want them counted.
- Asphalt shingles at 3 bundles per square unless you change it. Valleys, dormers and cross-gables add waste — raise the allowance.
- Ridge-cap and starter coverage vary by product (cap 20–33 lin ft/bundle, starter ~105 lin ft/bundle) — confirm against the wrapper.
- Ice-and-water shield, drip edge, flashing, vents and fasteners for those are separate.
- How many bundles of shingles do I need?
- Three bundles cover one square (100 ft²) for most shingles. Take your roof area in squares, multiply by 3, and add 10–15% for cuts, starter and ridge.
- Is this an exact order?
- It's a solid estimate. A supplier or roofer should confirm from the actual roof plan — hips, valleys and dormers change both the area and the waste.
Squares & bundles
1 roofing square = 100 ft² of roof surface. Universal roofing-trade convention (NRCA). 3 bundles per square for standard 3-tab and most architectural asphalt shingles. Asphalt Roofing Manufacturers Association (ARMA) / manufacturer packaging. Some heavy/designer shingles are 4–5 — adjust for your product.
Waste, nails, accessories
NRCA Roofing Manual and ARMA/ shingle-manufacturer application instructions (≈320 nails/square at 4 nails/shingle ≈ 2.5 lb; ridge/starter coverage per wrapper).
About the Roofing Calculator
The Roofing Calculator produces a full asphalt-shingle material list — squares, field bundles, underlayment rolls, starter strip, ridge-cap bundles and nails — from the roof footprint and pitch. It rolls together what the Roof Area, Roof Pitch and Roof Shingle calculators do individually, and adds the accessories. Ice-and-water shield, drip edge, flashing and vents are still separate, and a supplier should confirm the order from the real roof plan.
What you enter
- Roof footprint length
- Roof footprint width
- Roof pitch (rise-in-12) — Rise per 12 units of run. A low slope is 3–4; a steep roof is 9–12.
- Bundles per square — 3 for most 3-tab and architectural shingles; 4–5 for heavy/designer. Printed on the wrapper.
- Ridge + hip length — Total lineal feet of ridge and hips, for ridge-cap shingles. Leave 0 to skip.
- Eave + rake length — Perimeter lineal feet, for starter strip. Leave 0 to skip.
- Underlayment coverage per roll (squares) — Synthetic underlayment ≈ 10 squares/roll (1,000 ft²); #15 felt ≈ 4; #30 felt ≈ 2.
- Waste allowance — Default 10%. Adjust to your own allowance — the exact figure is always shown too.
What you get back
- Roof surface area — the exact result of the calculation.
- Roofing squares — shown as the exact figure and, separately, a recommended figure with your waste allowance added.
- Field shingle bundles — shown as the exact figure and, separately, a recommended figure with your waste allowance added.
- Underlayment rolls — the exact result of the calculation.
- Starter-strip bundles — ≈ 105 lineal ft per bundle of dedicated starter. 0 if you left eave + rake at 0.
- Hip / ridge cap bundles — ≈ 20–33 lineal ft per bundle of cap shingles; this uses 25 ft. 0 if you left ridge + hip at 0.
- Roofing nails — ≈ 2.5 lb per square at 4 nails/shingle (≈ 320 nails/square). Use 5–6 lb/square in a high-wind zone.
The formula, a worked example, the assumptions behind it and the sources are shown in full below the calculator.
Related calculators
- Roof Area Calculator — Sloped surface area of a simple gable or hip roof from its footprint and pitch.
- Roof Shingle Calculator — Shingle bundles and roofing squares for a roof of a given surface area.
- Roof Pitch Calculator — Roof angle, slope factor and rise-in-12 pitch from a rise and run.
- Roof Replacement Cost Calculator — Estimated cost to replace a roof from its area, material and labour rates.
Part of the Roofing calculators.