Hip roof calculator — hip rafters, jack rafters and four-slope geometry.
A hip roof adds diagonal geometry to the common-rafter calculation. The key is to keep common rafters, hip rafters, jack rafters and ridge geometry in the same model.
Calculate equal-pitch hip-roof geometry.
Enter the rectangular wall-line dimensions and roof pitch. The calculator assumes a regular full hip roof, equal pitch on all four sides and no overhang.
Why hip-roof geometry is different
A gable roof can be understood from one roof section. A hip roof also needs the plan geometry. The hip rafter does not run perpendicular to the wall; it crosses the corner diagonally, so its plan run is longer than the common-rafter run.
Hip rafter geometry
For a regular square corner, the plan run of the hip is the diagonal of the common-run square:
hip plan run = common run × √2
The actual sloping hip-rafter length must then include the roof rise in three-dimensional geometry.
Jack rafters
Jack rafters share the roof slope of the common rafters but terminate at the hip. Their lengths change in a regular sequence according to spacing and the hip geometry. A robust calculator should generate every jack position and length rather than ask the user to repeat the same calculation manually.
Ridge and roof dimensions
Building length, width, pitch and ridge arrangement determine where the hip rafters begin and how the roof surfaces meet. Real projects also need to account for section sizes and the exact reference lines used for cuts.
Hip roofs in Krokwio
Krokwio generates the framing across the four roof surfaces and keeps the common rafters, hip rafters and jack rafters connected to the same 2D/3D model. Openings can be assigned to the appropriate roof surface and element cards can be opened directly from the project.
Related: Hip Rafter Calculator, Jack Rafter Calculator, Roof Framing Calculator.
Turn roof geometry into workshop-ready information.
Use one project for geometry, 2D/3D views, element cards, cutting data, PDF documentation and QR identification.