Roof Pitch, Area, Hip/Valley & Panel Coverage

Pitch as x:12, degrees and percent; slope factor; sloped area from plan area; common rafter and hip/valley lengths from the run; standing-seam panel count and length.

Open the tool

Method

roof-geometry 1.1

Engine

1.1.0

Output status

Informational

Review

Awaiting review

Formulas

Slope factor = sqrt(1 + (p / 12)^2), p = rise per 12 of run
Sloped area = plan area x slope factor; rafter = run x slope factor
Hip or valley = run x sqrt(2 + (p / 12)^2) for equal-pitch planes meeting at 90 deg in plan
Panels = ceil(eave width / panel coverage); panel length = run x slope factor + overhang

Conventions

Run is the horizontal distance eave to ridge.
Degrees are measured from horizontal; 12:12 = 45 deg.

Limits - what it will not do

No minimum roof slope for any system is implied.
Pitches steeper than 89.9 deg are refused; above 24:12 a warning asks to check the input.

Who must review it

AFS estimator: panel coverage widths and overhang practice for the panels AFS supplies

Worked example

Inputs 6:12, 2,000 ft2 plan, 15 ft run, 40 ft eave, 16 in panels, 2 in overhang

Expected Slope factor 1.1180, 26.57 deg, 2,236.1 ft2, rafter 16 ft 9 1/4 in, hip 22 ft 6 in, 30 panels at 16 ft 11 1/4 in

Checked by an automated test on every change.

Sources

Right-triangle geometry (Pythagorean theorem and trigonometric ratios) - Method sheets roof-geometry/1.0 and geometry-conversion/1.0, read 2026-10-16
Slope factor = sqrt(1 + (rise/run)^2); a hip or valley between equal-pitch planes meeting at 90 deg in plan runs sqrt(2) x the common run, so its length factor is sqrt(2 + (rise/12)^2) per unit of common run.