Gambrel Roof Calculator
Calculate gambrel roof area, rafters, and cost.
Last updated: June 2026
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The length of the building along the ridge.
The span across the building (gable end).
Classic gambrel. Upper slope at 30°, lower at 60°.
Rafter Lengths
Upper rafter (per side)5.5 ftat 30° from ridge to break
Lower rafter (per side)14.4 ftat 60° from break to wall
Ridge length30 ft
Building footprint720 sq ft
Roof Area & Material Estimate
Total roof area1,317 sq ft(incl. 10% waste)
Roofing squares14(42 bundles)
Upper roof area333 sq ft
Lower roof area864 sq ft
Estimated roofing costAsphalt shingles, installed
$4,900 - $9,80014 squares × $350-$700/square
Based on: 30 × 24 ft building, 30° upper / 60° lower pitch. Asphalt shingle pricing from NRCA 2026. Last verified: June 2026.
Disclaimer: These estimates are for budgeting purposes only. Actual costs depend on your location, current material prices, and contractor rates. Always get 2-3 quotes from licensed contractors before starting any project.