Shingle Calculator – Understand Squares, Bundles & Pitch (Fast)
Use this shingle calculator to turn roof measurements into a clear shopping list. It converts your footprint into sloped roof area using the roof pitch factor, subtracts openings, applies a waste allowance, and returns both roofing squares (100 ft² units) and total bundles of shingles. Whether you’re ordering for a garage or a full re-roof, it answers the key question: “How many shingle bundles do I need?”
How the Shingle Calculator Works (Formulas)
- Plan area with overhangs:
(Length + 2 × rake) × (Width + 2 × eave) - Pitch factor:
√(rise² + 12²) / 12(for “rise per 12” pitch) - Sloped area:
plan area × pitch factor − openings - Waste applied:
sloped area × (1 + waste%)(e.g., 10–15%) - Squares:
area_ft² ÷ 100(1 square = 100 ft² ≈ 9.2903 m²) - Bundles:
ceil(area_ft² ÷ bundle coverage)(default 33.3 ft²/bundle)
Common Pitch Factors (quick reference)
4:12 → 1.054 · 6:12 → 1.118 · 8:12 → 1.202 · 10:12 → 1.302 · 12:12 → 1.414
Worked Example
Inputs: 40 ft × 24 ft building, 0.75 ft eave & rake overhangs, 6:12 pitch, 20 ft² openings, 10% waste, 33.3 ft²/bundle.
- Plan with overhangs:
(40 + 1.5) × (24 + 1.5) = 41.5 × 25.5 = 1,058.25 ft² - Pitch factor (6:12):
≈ 1.118 - Sloped (no waste):
1,058.25 × 1.118 − 20 ≈ 1,163 ft² - With 10% waste:
≈ 1,279 ft²→ Squares:≈ 12.8 - Bundles (33.3 ft²/bundle):
ceil(1,279 ÷ 33.3) = 39 bundles
What Affects Waste (Order Enough)
- Roof style & complexity: hips, valleys, dormers, and cut-heavy layouts increase offcuts.
- Steeper pitches: more pieces, more staging, typically a little more waste.
- Starter & ridge/hip caps: usually come from shingles but effectively add to total usage.
- Ordering: round up to whole bundles; keep 1–2 bundles for future repairs and color matching.
3-Tab vs Architectural Shingles
Both common asphalt shingle types typically figure at ≈3 bundles per square, but coverage per bundle can vary by brand. Architectural (laminate) shingles are heavier and often last longer; 3-tab are lighter and budget-friendly. Always check the bundle coverage printed on the wrapper and override the default if needed.
Underlayment, Nails & Flashings (Quick Guide)
- Underlayment: felt #15/#30 or synthetic; coverage varies by roll. Add a margin for laps and overlaps.
- Nailing: plan ~320 nails per square (4-nail) or ~480 nails per square (6-nail/high-wind).
- Drip edge & flashing: order by linear footage of eaves/rakes and penetrations (chimneys, skylights, vents).
- Ice & water shield: cold climates often require it at eaves/valleys—check local codes.
Pro Tip
Measure overhangs carefully. A small increase (e.g., 1.0 ft vs 0.5 ft) can add dozens of square feet across a roof.
Metric vs Imperial
1 roofing square (100 ft²) equals ≈ 9.2903 m². If you switch the unit system, the calculator keeps the math consistent, but bundle coverage should match the units you’re using (e.g., set bundle coverage to ≈3.09 m² for the common 33.3 ft²/bundle equivalent).
Safety & Planning
- Use proper fall protection on steep slopes and wet surfaces.
- Stage materials so you’re not over-loading trusses in one spot.
- Ventilation matters—verify intake/exhaust to protect shingle life.
Related Project Calculators
- Paver Calculator – plan walkways, patios, and approaches around the house.
- Epoxy Calculator – estimate epoxy coverage for garage floors and interiors.
- Fence Cost Calculator – budget your boundary or privacy upgrades.
Important Estimate Disclaimer
The results provided by this calculator are intended as general estimates only and should not be considered precise engineering measurements. Actual material requirements, costs, and quantities can vary significantly based on site conditions, local building codes, soil type, reinforcement requirements, climate exposure, and the intended use of your project.
These calculators are designed to help you plan and budget your project more effectively, but they do not replace professional advice from a qualified contractor, engineer, or building inspector. Always verify your calculations and assumptions with trained professionals before placing material orders or commencing construction.
For more information on the assumptions, formulas, and data used in these tools, see our Data Sources and Methodology pages.
Material estimates, cost figures, and volume calculations are approximate and may not reflect your actual requirements. Always double-check dimensions and project-specific needs, and consider adding a contingency allowance for waste, over-excavation, and unforeseen conditions.
If you are unsure about any aspect of your project — including structural requirements, reinforcement needs, drainage, or load-bearing capacity — consult with a licensed professional before proceeding.