Hip and Valley Factor
The hip and valley factor is determined by finding the square root of ((rise/run)² + 2).
The hip and valley factor is a number that is multiplied by the actual run (horizontal distance) of a common rafter to determine the length of a hip or valley rafter. Repeat, the actual run, not the length, of a common rafter. The hip and valley factor varies according to the slope of the roof, as shown below.