Free Hip Roof Calculator — Rafters, Area & Materials (2026)

How to Use This Calculator

1. 1Measure the overall building length and width in feet.
2. 2Enter the roof pitch (rise per 12 inches of run).
3. 3Select your rafter spacing (16" OC is standard).
4. 4Click Calculate for rafter counts, hip rafter length, roof area, and ridge length.

About This Material

A hip roof has four sloped sides — two triangular ends and two trapezoidal sides — all meeting at a central ridge that is shorter than the building length. Because every wall is protected by an eave overhang, hip roofs offer superior wind resistance (they can withstand 110+ mph winds better than gables) and are preferred in hurricane-prone regions and areas with high wind exposure. Hip roofs are more complex to frame than gable roofs, requiring four hip rafters that run diagonally from each corner to the ridge, king common rafters centered on each triangular end, and numerous jack rafters that run parallel to the common rafters but are progressively shorter as they approach each hip. The hip rafter is typically one size larger than the common rafters (e.g., 2x10 hip with 2x8 commons) because it carries loads from jack rafters on both sides. Hip rafters require compound angle cuts (a combination of plumb cut and cheek cut) that are more demanding to execute than standard rafter cuts. The ridge board on a hip roof runs only from where the two hip rafters on each end converge, so the ridge length equals the building length minus the building width. Jack rafters are cut with a compound miter at the hip rafter end and a standard bird's mouth at the wall plate. For a typical 30x40 ft hip roof at 6/12 pitch, material costs run $3,000 to $6,000 for framing lumber alone, with professional framing labor adding $4,000 to $8,000.

Installation Tips

• •Frame hip rafters from 2x stock one size deeper than common rafters for adequate bearing.
• •Use a framing square or construction calculator to determine jack rafter compound angles.
• •Install hip rafters first, then fill in jack rafters from longest to shortest.
• •Bevel the top of hip rafters (drop the hip) so sheathing lies flat across the hip line.
• •Brace hip rafters temporarily until sheathing is installed — they can twist under their own weight.

Common Mistakes to Avoid

• ⚠Using the same lumber size for hip rafters as common rafters — hips carry double the load and need to be one size deeper.
• ⚠Not accounting for the hip rafter drop or bevel — sheathing will not lie flat and creates a hump at the hip.
• ⚠Forgetting that jack rafters require compound angle cuts, not simple plumb cuts.
• ⚠Underestimating material — hip roofs use 10–15% more lumber and sheathing than an equivalent gable roof.

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