Hip rafter calculator — length, plan run and three-dimensional geometry.

Step 1: common run

Start with the horizontal common-rafter run from the wall/support reference to the ridge reference. On a simple symmetrical roof this is derived from the building width and ridge position.

Step 2: diagonal plan run

At a square corner:

hip plan run = √(common run² + common run²)

which simplifies to common run × √2.

Step 3: true sloping length

The hip rafter rises by the same vertical roof rise as the surrounding roof surfaces. The spatial length therefore comes from the diagonal plan run and that rise:

hip length = √(hip plan run² + rise²)

Why workshop geometry is more than one length

A hip rafter can require bevels, drops or chamfers depending on how the surrounding rafters meet it and how the project is detailed. That information belongs on the element card with a clearly defined orientation and reference system.

Hip rafters in Krokwio

Krokwio treats the hip rafter as part of the complete hip-roof model. The element can be selected in 2D or 3D and connected to its card, dimensions and project documentation.

Related: Hip Roof Calculator, Jack Rafter Calculator.