Roof Pitch to Degrees Converter
This free roof pitch to degrees converter turns a roof pitch like 6/12 into its angle in degrees, slope percent, rafter length factor, and a steepness category. You can also run it in reverse: enter an angle in degrees and get the matching X/12 pitch back.
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Your results
| Pitch ratio | — |
| Rafter length factor (per ft of run) | — |
| Steepness category | — |
Steepness categories are general guidance only, not building-code advice — always follow local code and the manufacturer's installation specs.
How to use this calculator
Roof pitch is written as X/12: the number of inches the roof rises for every 12 inches of horizontal run. Set the rise (default 6) with the number field or the slider, and the angle, slope percent, pitch ratio, rafter length factor, and steepness category update instantly. The rise slider covers 0 to 24 inches of rise.
Working backward from a measured angle? Switch to Degrees → Pitch mode and type the angle. The tool converts it to the matching X/12 pitch plus all the same supporting numbers, so you can walk from a roof measurement app or an angle finder straight to the pitch a shingle or truss guide expects.
How it works
The geometry is a right triangle with a fixed 12-inch horizontal run. The angle at the base is angle = arctan(rise ÷ 12), converted from radians to degrees. The slope percent is simply (rise ÷ 12) × 100%, and the pitch ratio is the rise written as X:12.
The rafter length factor comes from the Pythagorean theorem: the rafter is the hypotenuse of the triangle, factor = √(12² + rise²) ÷ 12. That factor is the rafter length per foot of horizontal run — multiply it by your roof's horizontal run to get the rafter length. These are exact geometric results; the steepness category (flat, low, medium, steep) is an estimate, labeled as general guidance only.
Frequently asked questions
What does a 6/12 roof pitch mean in degrees?
A 6/12 roof pitch means the roof rises 6 inches for every 12 inches of horizontal run. Converted to an angle, that is arctan(6/12), which is about 26.6 degrees. A 6/12 pitch is in the medium steepness range.
How do you convert roof pitch to degrees?
Divide the rise by 12 to get the slope as a decimal, then take the inverse tangent (arctangent) and convert radians to degrees: angle = arctan(rise / 12) x (180 / pi). For example, an 8/12 pitch gives arctan(0.667), which is about 33.7 degrees.
What is the difference between roof pitch and roof slope?
Roof pitch is usually written as rise over a fixed 12-inch run, like 6/12. Roof slope is the same ratio expressed as a percentage, like 50%. Roof angle is the same geometry expressed in degrees. They all describe the same steepness, just in different units.
What is the rafter length factor for roof pitch?
The rafter length factor is the length of rafter needed per foot of horizontal run. It is calculated as sqrt(12^2 + rise^2) / 12. Multiply it by the horizontal run of the roof to estimate rafter length. For a 6/12 pitch, the factor is about 1.118, so a 10-foot run needs roughly an 11.18-foot rafter.