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Roof pitch calculator
Enter vertical rise and horizontal run to calculate roof pitch, slope percentage, angle and approximate rafter length.
How do I calculate roof pitch?
Measure the vertical rise and horizontal run in the same unit. The calculator reports rise per 12 units of run, slope percentage, angle in degrees and radians, and the sloping rafter length. Add an optional horizontal eave overhang to include it in the rafter-length estimate.
Frequently asked questions
How do I calculate roof pitch?
Measure the vertical rise and horizontal run in the same unit. The calculator reports rise per 12 units of run, slope percentage, angle in degrees and radians, and the sloping rafter length. Add an optional horizontal eave overhang to include it in the rafter-length estimate.
Are roof measurements uploaded?
No. This geometry calculation runs in your browser and does not send measurements to a server.
What does a 12:12 roof pitch mean?
It means the roof rises 12 units vertically for every 12 units of horizontal run, which is a 45-degree angle.
Does the rafter-length estimate include overhang?
Only if you enter a horizontal eave overhang. The estimate uses a straight right triangle and does not account for cuts, ridge board, fascia or framing details.