What does the barn roof (gambrel) calculator estimate?

Ridge and break heights, rafter lengths for lower/upper segments, frame counts by spacing, roof area, and 4x8 sheathing. It is a planning estimator only, not a structural design tool.

How accurate are the results?

This calculator uses geometric approximations. Engineered drawings can vary due to heel height, web layout, plumb cuts, and connection details.

🏚️ Barn Roof (Gambrel) Calculator

Plan gambrel geometry: heights, rafter lengths, frame counts, roof area & sheathing. Not a structural design tool — use engineered drawings for permits.

Building Width (ft) Eave-to-eave width (without overhangs).

Building Length (ft) Used to count frames/bents by spacing.

Lower Pitch (rise:12) Steeper lower slope (e.g., 7–10:12).

Upper Pitch (rise:12) Shallower upper slope (e.g., 3–6:12).

Break Position (% of half-span) 0.40 means the break is 40% of half-span from the eave.

Overhang (in, per eave) Horizontal eave overhang.

Frame Spacing (in) Typical: 16, 19.2, 24.

Results will appear here

📌 Enter width & length, lower/upper pitches, break %, overhang, and spacing.