VYRCO / Quality and measurement

Cp and Cpk indices

Calculate capability indices from limits, a mean and an estimate of sigma.

Free · no accountv1.0 · 2026-10-10Private inputs in your browser

Cp and Cpk indices

VYRCO · v1.0 · https://vyrco.com/en/tools/process-capability/

Input data

Numbers: use a decimal point or comma, without thousands separators. Complete fields unless marked optional.

Preparing the tool…

Your inputs are processed here and are not sent to VYRCO. There is no autosave: download your project before closing or switching languages. Opening JSON reads a local file; it does not upload it. CSV includes inputs and results. For PDF, use Print / PDF and select Save as PDF.

How to use it

Use limits, mean and sigma in the same unit.
Separately check stability, distribution and sigma estimation.
Calculate indices and apply the specific criterion agreed for your study.

Fictional example

Fictional data: Cp ≈ 1.667 and Cpk ≈ 1.333. These are numeric results, not an approval.

Method

Cp = (USL − LSL)/(6σ). Cpu = (USL − mean)/(3σ). Cpl = (mean − LSL)/(3σ). Cpk = min(Cpu, Cpl).

Scope and limitations

Usual interpretation assumes a stable process and an approximately normal distribution. This tool does not verify those assumptions or sigma quality, estimate rejects, or impose universal thresholds.