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Calculate rafter length from span, pitch, and overhang. Get rafter run, rise, diagonal length, and birdsmouth cut dimensions for roof framing.
Calculate asphalt shingles needed for your roof. Enter roof area and bundle coverage to get shingle bundles, squares, and waste allowance for reroofing.
Complete roofing material takeoff: shingles, underlayment, drip edge, nails, and ice shield. Enter roof area and pitch for full replacement material list.
US convention expresses pitch as inches of rise per 12″ horizontal run. A 4/12 pitch rises 4″ for every 12″ of run.
Pitch = Rise ÷ Run (expressed as X/12)Multiply footprint area by pitch factor to get true roof surface area. 4/12 pitch factor ≈ 1.054.
Pitch Factor = √(1 + (Rise/Run)²)Convert pitch to degrees for rafter cuts and to percent slope for drainage and code minimums.
Angle (°) = arctan(Rise/Run); Slope % = (Rise/Run) × 100Updated: July 2026
1,500 sq ft footprint × 1.054 pitch factor = 1,581 sq ft roof area for shingle and underlayment orders.
8/12 pitch equals 33.7° — use for miter saw settings on rafter tails and fascia angles.
2/12 (9.5°) is minimum for many rolled roofing products. Verify against manufacturer and local code before low-slope install.
Convert between roof pitch notation (rise over 12″ run), angle in degrees, and slope percent for roofing and construction. Enter rise and run to get pitch factor for converting footprint area to actual roof surface area.