How roof pitch is expressed
Roof pitch compares the vertical rise to a horizontal run. In imperial building terms it is often written as rise per 12 units of run, such as 6:12. The roof angle shows the same slope in degrees.
Measure your roof
Measure the vertical rise from the wall plate to the ridge and the horizontal run from the ridge centre to the outside wall. For a simple gable roof, enter the building length to estimate one roof slope.