Shingle Calculator – Understand Squares, Bundles & Pitch
Use this shingle calculator to turn roof measurements into a clear shopping list. It converts your footprint into sloped roof area using a pitch factor, subtracts openings, applies a waste allowance, and returns roofing squares (100 ft² units) and bundles of shingles.
What this calculator includes vs. doesn’t include
- Includes: footprint + overhangs, pitch factor, openings subtraction, waste, squares, bundles.
- Doesn’t include: ridge/hip cap bundles, starter strip, underlayment rolls, ice & water shield, step flashing, drip edge.
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 ÷ 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
Metric vs Imperial (bundle labels)
1 roofing square (100 ft²) equals ≈ 9.2903 m². If your bundle is labeled 33.3 ft², keep 33.3 and use Imperial. If you prefer metric input, set bundle coverage to ≈ 3.09 m² (same bundle).
Related Roofing Calculators
Shingle Calculator FAQ
How many bundles are in a roofing square?
A roofing square is 100 ft². Many asphalt shingles work out to about 3 bundles per square, but coverage can vary by brand and product. Always check the wrapper and adjust “bundle coverage” if needed.
What waste percentage should I use for a hip roof?
Hip roofs often need more waste due to cut-heavy hips/valleys. A common range is 12–15%, and complex roofs with dormers/valleys may need more.
Does roof pitch change roof area?
Yes. A steeper roof has more sloped surface area than its footprint. This calculator uses a pitch factor based on rise-per-12 to convert plan area to sloped area.
Should I subtract skylights, chimneys, and other openings?
Usually yes for larger items. Small penetrations and cut waste may cancel out, but large skylights/chimneys can be worth subtracting. This tool clamps extremely large opening values to avoid negative area.
How do I estimate ridge cap bundles?
Ridge/hip caps aren’t included in the bundle count here. Manufacturers list ridge-cap coverage per bundle (linear feet). Measure ridge/hip length and use the wrapper’s cap coverage to estimate additional bundles.
Accuracy & Review
Reviewed by: Caleb Wright
Caleb validates our roofing calculators, reviewing shingle coverage assumptions, waste factor guidance, and pitch-factor formulas to help ensure estimates reflect common real-world installation conditions.
Last updated:
See: Methodology · Data Sources · Review Board
Important Estimate Disclaimer
Results are preliminary estimates only and do not replace professional roofing specifications. Material quantities may vary based on pitch complexity, waste factors, underlayment layers, and local code requirements.
Review our Methodology and Data Sources for calculation details.
Wind exposure, flashing requirements, and structural considerations may affect final material totals.