Roofing Calculator

Footprint Length (ft)

Footprint Width (ft)

Pitch Rise (inches per 12")

Slope factor = √(rise²+12²)/12 is applied to plan area.

Waste (%)

Covers off-cuts, starter/course, defects. Adjust for complexity.

Eave Overhang (in)

Adds to width on both eave sides.

Rake Overhang (in)

Adds to length on both rake sides.

Additional Plan Area (sq ft)

Garages, porches, dormers. Adds to plan area before slope.

Bundles per Square

Typical 3; confirm on your shingle label.

Underlayment Coverage per Roll (sq ft)

Net coverage after overlaps. Check product spec.

Ridge Length (ft)

For ridge-cap estimate; set 0 if unknown.

Ridge-Cap Coverage per Bundle (ft)

Varies widely by product; read the bundle label.

Drag & drop a small CSV/TSV to prefill fields (no upload; parsed in your browser). Expected headers: length_ft,width_ft,rise_in,overhang_eave_in,overhang_rake_in,waste_pct,extra_sqft,bundles_per_square,roll_coverage_sqft,ridge_len_ft,ridge_cap_per_bundle_ft

Roofing Calculator – Quick Cheat Sheet

Pitch factor: √(rise² + 12²) ÷ 12. Multiply plan area by this to get sloped area.
Squares: sloped area ÷ 100.
Bundles: squares × bundles_per_square × (1 + waste%); round up.
Underlayment rolls: sloped area × (1 + waste%) ÷ roll_coverage; round up.
Overhangs: Eave adds to width (both sides), rake adds to length (both sides).
Ridge-cap: ridge length ÷ coverage per bundle; round up.
Perimeter: simple drip-edge estimate = 2 × (plan length + plan width) including overhangs.
Reality check: Coverage values (bundles/square, ridge-cap/bundle, roll coverage) vary by product; use your label.

Notes & edge cases

Complex roofs (hips, valleys, multiple sections) typically need higher waste% (e.g., 12–20%+). Adjust accordingly.
This tool treats extra areas as flat plan area added before pitch. For many small sections, estimate each and sum.
All math is unit-consistent (feet/inches). Nothing is uploaded; CSV parsing happens in your browser only.

Roofing Calculator

Roofing Calculator – Quick Cheat Sheet

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