What is roof pitch, and how do I find mine?
Short answer. Roof pitch is the steepness of a roof written as rise over run: how many inches it rises for every 12 inches it extends horizontally, such as 4/12 or 8/12. You can find yours from the attic with a level and tape measure, from across the street with a phone angle app, or from the measurement report on a roofing estimate.
Pitch vs slope
Strictly speaking, slope is rise per 12 inches of run and pitch is rise over the full span, but nearly every roofer uses pitch to mean the 12-inch version. You will see it written as 6/12, 6:12, or simply "a six pitch."
Three ways to measure your own
- In the attic: hold a level horizontally against the bottom edge of a rafter, mark 12 inches along the level, and measure straight up from that mark to the rafter. That number is your rise: 7 inches means a 7/12 roof.
- At the rake edge: do the same against the sloped edge of the roof from a ladder, only if you are comfortable up there.
- From the ground: angle finder apps read the roofline from across the street. Convert degrees to pitch with a chart: about 18 degrees is 4/12, about 27 is 6/12, about 34 is 8/12.
Why your roofer cares
- Materials: shingles need at least 2/12, with extra underlayment below 4/12.
- True area: a pitch factor multiplies the flat area, about 1.12 at 6/12 and 1.41 at 12/12.
- Safety and labor: roofs steeper than about 7/12 need roof jacks and harnesses and often carry a steep charge.
Most houses have more than one pitch, such as a 6/12 main roof with 12/12 front gables, and a good measurement report lists each section. How roofers measure a roof explains the rest, and roof anatomy explained names the parts you will be measuring.