Frequently Asked Question
The angle, or pitch, of a roof is calculated by the number of inches it rises vertically for every 12 inches it extends horizontally. For example, a roof that rises 6 inches for every 12 inches of horizontal run has a 6/12 pitch.
The first number denotes the vertical (height) and the second number denotes the horizontal (length). So, a roof pitch of 5/12, which also happens to be a common roof pitch, means that for every 12 feet, the roof drops 5 feet (or rises 5 feet, however you choose to look at it—same thing).
Extremes range from zero to 12/12. More likely, you will find roof pitches in the range of 4/12 up to 8/12.