Gambrel Roof Calculator

Calculate rafter lengths, pitch angles, and roof area for barn-style gambrel roofs. Perfect for sheds, barns, and Dutch colonial homes.

🏠 Building Width (feet)

Total span from eave to eave

📐 Lower Slope Pitch (rise / run)

📐 Upper Slope Pitch (rise / run)

📍 Break Point (% of half-span where lower slope ends)

Percentage of half the building width where lower rafter meets upper rafter

📏 Eave Overhang (inches)

📐 Roof Ridge Length (feet) — length of building

🔄 Waste Factor (for roofing materials)

🏚️ Gambrel Roof Calculations

0 sq ft

Includes lower & upper rafter lengths + total roof area.

🏗️ Gambrel roof geometry: Two different slopes per side — steeper upper, gentler lower. Maximizes headroom in barns and sheds.

📐 Pro tip: Standard barn gambrel uses 5:12 lower and 12:12 upper pitch. Add 10-15% waste for shingles or metal roofing.