How to Measure a Hip Roof
Collect the right measurements for a hip roof so the calculator returns a usable area and rafter lengths.
Good inputs make a good estimate. A hip roof calculation needs four things: the building length, the building width, the roof pitch and the horizontal eave overhang. The order you measure them in matters less than being consistent about whether your dimensions are wall lines or outer eaves.
Step 1: Choose wall or eave measurements
Measure the outside of the exterior walls for wall-line dimensions, or the outer edge of the eaves for eave-to-eave dimensions. Write down which one you used. In the calculator, set the measurement basis to match. If you measured walls, the tool adds the overhang; if you measured eaves, it does not.
Step 2: Measure the horizontal overhang
The overhang is the horizontal distance the eave projects past the wall, measured level, not along the slope. A 12-inch overhang means the eave is one foot beyond the wall on that side. The calculator assumes the same overhang on all four sides of a regular hip.
Step 3: Get a consistent rise reference
Determine the pitch with a level and a tape, or from the building plans. Measure 12 inches horizontally and the vertical drop to the roof is the rise in X/12. Keep the same reference for every face; a regular hip assumes one equal pitch throughout.
Ground-level and plan alternatives
You do not need to climb a steep or wet roof to estimate area. You can take the footprint from the ground, read the overhang from the eave projection, and get the pitch from the gable end or the plans. Leave roof access to people with proper equipment and training.
Measurement checklist
- Length and width, with a note of wall vs eave basis
- Horizontal overhang (level distance past the wall)
- Pitch as X/12, degrees or a measured rise and run
- Whether all faces truly share one equal pitch
- Any dormers, valleys or additions to measure separately
With those in hand, open the hip roof calculator and enter them in the matching basis. For complex shapes, measure each sloped face and use the roof area calculator in measured-plane mode.