Measure the vertical rise over a 12-inch horizontal run
Use the formula: pitch = rise รท run
Express roof pitch as inches of rise per 12 inches of run
Example: 6 inches of rise over 12 inches of run = 6/12 pitch
Convert pitch to slope if needed: slope = rise/run
Convert pitch to angle if needed: angle = arctangent(rise/run)
Use a level and tape measure to find the rise and run
Mark 12 inches horizontally, then measure the vertical rise at that point
Record the result as a fraction, ratio, or angle as required