Roof Pitch and Slope Calculator
Enter the rise and run of your roof to get the pitch as an x:12 ratio, the angle in degrees, the slope factor and the percent grade. Add a run to size the rafter.
How to find roof pitch
- Measure the vertical rise over a set horizontal run, usually 12 inches.
- Enter the rise and run in inches.
- Read the x:12 ratio, angle, slope factor and grade.
- Enter a horizontal run in feet to get the rafter length.
Examples
A 6:12 roof
rise 6 in over run 12 in
6:12 ratio, 26.57 degrees, 1.118 slope factor, 50% grade
Frequently asked questions
What does a 6:12 roof pitch mean?
It means the roof rises 6 inches for every 12 inches of horizontal run. That works out to about 26.57 degrees and a 50 percent grade.
How do I convert roof pitch to degrees?
Take the arctangent of rise divided by run. For 6:12 that is arctan(6/12), which is 26.57 degrees. This tool does it instantly.
What is the slope factor used for?
Multiply the horizontal run by the slope factor to get the rafter length and the true sloped roof area for ordering shingles.
How do I measure roof pitch safely?
Hold a level horizontally against a rafter, mark 12 inches along it, then measure straight down to the roof at that point. That drop is the rise.
What is a low slope versus a steep roof?
Pitches below 4:12 are low slope and shed water slowly. Pitches of 9:12 and above are steep and usually need extra fall protection to work on.
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