Gambrel Roof Calculator
Construction & Home ImprovementCalculate rafter lengths, roof area, and attic volume for a two-pitch gambrel (barn-style) roof.
Total Roof Area
Total roof area across all four gambrel roof planes.
Approximate Attic Volume
3,597
Approximate usable volume enclosed by the gambrel roof shape.
Lower Rafter Length
8.81
Length of each lower-slope rafter.
Upper Rafter Length
7.24
Length of each upper-slope rafter.
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Construction & Home Improvement calculators
Calculator Stats
Creators
Odeh Ahwal0people find this calculator helpful
Views
Helpful
Saved
Embeds
Construction & Home Improvement calculators
Frequently Asked Questions
What is a gambrel roof?
A gambrel roof, the classic barn-style roof, has two pitches on each side: a steep lower slope and a shallower upper slope. This shape maximizes usable interior space, such as a loft or attic, compared to a single-pitch roof.
Why enter angles instead of a rise and run pitch ratio?
Gambrel roofs are commonly specified as two independent slope angles rather than a single x-in-12 ratio, since the whole design comes from combining a steep lower angle with a shallower upper angle. Enter the angle for each slope directly.
How accurate is the attic volume figure?
This gives the volume of the roof cross-section shape extended along the building length, a good approximation for the enclosed space. It does not subtract for interior framing, insulation, or a flat ceiling plane if one is added below the roofline.
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