Roof pitch describes how steep a roof is, written as rise over run — the inches a roof rises for every 12 inches it runs horizontally. A “6/12 pitch” rises 6 inches per foot, and that one number drives material quantities, walkability, and which shingles you can use.
How to measure it
Hold a level horizontally against the roofline and mark 12 inches along it. Measure straight down from that 12-inch mark to the roof — that vertical distance is your rise. A 12-inch level with a 5-inch drop is a 5/12 pitch.
The math
Pitch is rise ÷ run, expressed per 12. To convert to degrees, take the arctangent of rise ÷ run. To find true sloped area from the building footprint, multiply by a pitch multiplier.
Worked example
A roof over a 40 ft × 30 ft footprint (1,200 sq ft) at 6/12 pitch has a multiplier of √(36 + 144) ÷ 12 = 1.118. Actual sloped area ≈ 1,200 × 1.118 = 1,342 sq ft before waste and overhangs.
Pitch reference chart
| Pitch | Angle | Area multiplier |
|---|---|---|
| 3/12 | 14.0° | 1.031 |
| 4/12 | 18.4° | 1.054 |
| 6/12 | 26.6° | 1.118 |
| 8/12 | 33.7° | 1.202 |
| 12/12 | 45.0° | 1.414 |
Pitches under 3/12 are “low slope” and need special membranes rather than standard shingles. Anything 8/12 and steeper usually requires roof jacks to walk safely.
Frequently asked questions
What is a good roof pitch? Most homes fall between 4/12 and 9/12 — steep enough to shed water and snow, shallow enough to build economically.
Can I measure pitch from the ground? Yes, approximately — photograph the gable end square-on and measure rise and run off the photo.
Why does pitch matter for materials? Steeper roofs have more surface area per square foot of footprint, so they need more shingles and underlayment.