Cp is a measure of process capability that compares the specification width (USL – LSL) to the total process variation (6σ) for a given process or product parameter. The higher the Cp value, the more potential a process has to fit inside specification limits. Unlike Cpk, Cp does not take the process position (mean) into account, so a high Cp does not necessary equate to a capable process. The equation for Cp is
Note that for a perfectly centered process, Cp = Cpk.