Roof Pitch Calculator
Convert roof rise and run into pitch, angle and slope factor.
Roof pitch describes how steep a roof is. This tool converts between the 'rise in 12' notation, the angle in degrees, and the slope factor used to turn a flat footprint into actual roof area.
How the Math Works
The Roof Pitch Calculator uses fundamental trigonometry to convert roof dimensions. The angle is calculated using the arctangent function (atan) of the rise divided by the run, which gives the roof's slope angle in degrees. The slope factor, also known as the pitch factor, is derived from the Pythagorean theorem: the square root of (rise squared plus run squared) divided by the run. This represents the multiplier needed to convert horizontal measurements to actual roof surface lengths.
Practical Applications
To use this calculator for a roof repair project, first measure the vertical rise from the roof deck to the ridge and the horizontal run from the same point to the outside wall plate. Enter these measurements to instantly determine your roof's pitch angle for ordering materials with correct specifications, calculate the slope factor for estimating roofing square footage, and verify your roof meets local building code requirements for wind and snow load resistance.
Day-to-Day Use
This calculator helps homeowners and contractors make critical decisions when selecting roofing materials, planning gutter installations, or estimating repair costs. Knowing your roof angle helps determine if it's suitable for solar panel installation, while the slope factor is essential for ordering the correct amount of shingles, tiles, or metal roofing panels. It also aids in selecting appropriate safety equipment and fall protection systems based on roof steepness.
Worked example
Rise 6 in over run 12 in → pitch 6/12, angle 26.57°, slope factor 1.118.
FAQ
What is a 'good' roof pitch?
4/12 to 9/12 is common for shingled roofs; below 2/12 needs special low-slope materials.