Roof Pitch Calculator
Convert rise/run to degrees and check walkability safety.
Measurements
in
in
Standard run is 12 inches.
Understanding Roof Pitch
Roof pitch is calculated as "Rise over Run." In the US, the run is standardized to 12 inches.
So a "4/12 pitch" means for every 12 inches the roof goes horizontally, it rises 4 inches vertically.
Common Pitches
- Low Slope: 1/12 to 3/12. Requires specialized rolled roofing or membranes. Shingles can leak.
- Walkable: 4/12 to 6/12. Standard range for most suburban homes. Can be walked on carefully.
- Steep: 7/12 to 9/12. Difficult to walk on. Requires traction aids.
- Non-Walkable: 10/12 to 12/12. Extremely steep. Do not attempt without professional safety gear.
FAQ
What is a standard roof pitch?
A standard gable roof usually has a pitch between 4/12 and 9/12. Anything below 3/12 is considered a low-slope or flat roof and requires special membrane roofing instead of shingles.
How do I calculate rafter length?
Take the total horizontal run of the rafter span and multiply it by the 'Length Multiplier' shown above. For example, if your run is 10 feet and the multiplier is 1.054, the rafter length is 10.54 feet.
Is my roof safe to walk on?
Generally, pitches up to 6/12 are considered walkable for experienced workers. Pitches from 7/12 to 9/12 are steep and dangerous. anything over 10/12 is non-walkable and requires harnesses and roof jacks.
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