Cpk Process Capability Calculator
Online Cpk process capability calculator. Calculate Cp, Cpk, Pp and Ppk with a normal distribution histogram and sigma level assessment. Meets ISO 9001 / IATF 16949 requirements.
What Cpk value is considered acceptable?
A Cpk ≥ 1.33 (equivalent to a 4σ level) is the common requirement. In the automotive industry under IATF 16949, initial process capability typically requires Cpk ≥ 1.67, and ongoing production requires Cpk ≥ 1.33.
What is the difference between Cp and Cpk?
Cp measures process precision (spread) and ignores any shift of the mean; Cpk accounts for both spread and mean shift. Cpk = Cp × (1 − k), where k is the offset (centering) factor.
What is the difference between Cpk and Ppk?
Cpk estimates process variation from the within-subgroup standard deviation, while Ppk uses the overall standard deviation. Cpk suits processes in statistical control; Ppk suits early-stage processes or smaller data sets.