Calculate Cp and Cpk online: enter mean, standard deviation, LSL and USL to get the process capability index with interpretation (AS9103 / IATF). Free, no sign-up.
Process capability (Cp and Cpk) is a statistical measure of a manufacturing process's ability to produce parts within specified tolerances. Cp assesses potential dispersion (tolerance range divided by 6σ), regardless of centering. Cpk additionally accounts for the offset of the process mean from the tolerance center — making it the true indicator of actual process performance.
Per AS9103 (the process capability companion to AS9102), Cpk ≥ 1.67 is required for Key Characteristics in production. A Cpk below 1.00 means the process is producing out-of-tolerance parts. This calculator outputs Cp, Cpk, and an immediate interpretation of the capability level per AS9103 and IATF 16949, from the mean, standard deviation, upper tolerance limit (USL), and lower tolerance limit (LSL).
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