roof pitch calculator

Roof pitch describes how steep a roof climbs by comparing the vertical rise to the horizontal run. Builders express it as a ratio such as 6 in 12, meaning the roof climbs six inches for every 12 inches of run. Accurately converting that ratio into slope angle, rafter length, and surface area helps estimate materials, verify code compliance, and plan safe installation angles for shingles or standing seam panels.

How to Use the Calculator

Measure the vertical rise from the top of the rafter to the bottom plate in inches, then measure the horizontal run from the exterior wall to the centerline of the ridge in inches. Enter the length of the roof along the ridge in feet, which helps determine surface area for a simple gable roof with two identical sides.

Example

A roof with a 90-inch rise, 180-inch run, and a ridge length of 42 feet produces a pitch of 6 in 12, a slope angle near 26.57°, a rafter length of 20.10 feet for each side, and an estimated total surface area of roughly 1690 square feet.

This information guides fastening schedules, snow load checks, and how many bundles of shingles or sheets of metal are required before crews step on site.