Roof pitch & area

Inclination is rise divided by horizontal run: percent = 100 × rise/run; angle = atan(rise/run); rise per 12 = 12 × rise/run. Both lengths use the same unit. For example, 1 m rise over 2 m run gives 50%, 6/12 and about 26.565°. The horizontal run is not the sloping roof length. A 100% slope is 45°, not 90°. Zero inclination is allowed. Changing the input mode converts a valid value; an invalid value is cleared.

Optional roof geometry assumes a symmetric gable with equal slopes and a central ridge, or one planar mono-pitch surface. Building width is across the slope, building length runs along the ridge. These default dimensions are examples. Both roof types use the same angle on their entire surface.

Overhangs are measured horizontally. The eaves amount applies to each edge across the slope (both lower and upper edges for a mono-pitch roof); the end amount applies to each end along the ridge. Roof plan area = (width + 2 × eaves) × (length + 2 × end). Total sloped area = roof plan area / cos(angle). Gable slope length = (width/2 + eaves) / cos(angle); mono-pitch length = (width + 2 × eaves) / cos(angle). Rise above the building walls excludes overhangs: width/2 × tan(angle) for gable, width × tan(angle) for mono-pitch.

The result is geometric surface area, not material order quantity. No waste, overlaps, dormers, openings, hips, unequal slopes or structural design. Slope length is not a cut list for rafters and includes no allowances for joints or cuts. For total area with unequal overhangs, use half their combined horizontal distance per direction. The per-side gable slope length assumes equal eaves overhangs. Length-field bounds are software limits; very steep or extreme values can exceed numeric precision. Nothing is stored.