Roof Pitch Calculator
Turn a measured rise and run into roof pitch, the angle in degrees, the slope percentage, and the rafter length you need to cut.
Measure the rise, how far the roof goes up, over a known run, how far it goes across. Pitch is normally written as rise per 12 inches of run, so a roof that rises 6 inches over 12 is a 6/12. If you enter a half-span, the distance from the outside wall to the ridge, you also get the rafter length along the slope.
| Slope percentage | |
| Angle | |
| Rafter length |
Geometry only. Rafter length is the sloped distance and does not include overhang, ridge board thickness, or birdsmouth adjustments.
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Once you know the pitch, price the job and count materials.