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FREE QUALITY TOOL

Process Capability Analyzer

Cp = (USL - LSL) / 6sigma; Cpk = min[(USL - mean), (mean - LSL)] / 3sigma

INPUT DATA

Enter calculation values

Select the unit for each measurement. Compatible values are converted automatically before calculation.

CALCULATED RESULT—

The result updates as valid values are entered.

Unit handlingCompatible units are normalized internally. Confirm units, assumptions and significant figures before use.

CALCULATION GUIDE

Understand your calculation

Clear inputs, a practical example and the context you need to interpret your result.

How it works

Cp = (USL − LSL)/(6s); Cpk = min(USL − mean, mean − LSL)/(3s).

Inputs and units

Enter all four values on the same scale. Mean and limits may be zero or negative; standard deviation must be positive and USL must exceed LSL.

Worked example

Mean 10, s 1, LSL 4, USL 16: Cp = 12/6 = 2.000; Cpk = min(6,6)/3 = 2.000.

Interpreting the result

Cp describes potential spread relative to specifications; Cpk also reflects centering. A negative Cpk means the mean lies outside a limit.

Assumptions and limitations

Assumes a stable process and a suitable distribution and variation estimate. The tool cannot distinguish within-process sigma from overall SD; using overall SD generally corresponds to Pp/Ppk. No capability acceptance decision is made.