Understanding Roof Pitch, Rafter Lengths & Slope Angles

In roof framing and shingle estimation, roof pitch is stated as the ratio of vertical rise over a constant 12-inch horizontal run (e.g. 4:12, 6:12, or 8:12). Pitch dictates the type of roofing materials allowed by building codes (e.g. asphalt shingles require at least a 2:12 pitch).