CpK (Process Capability)
Last updated: September 8, 2026
CpK is a calculation tool. It performs standard process capability and statistical process control calculations (Cp, Cpk, Pp, Ppk, control charts, normality testing) based on the data you enter, speak, scan, or capture live from a machine display. This page explains the limits of what that means in practice.
Every calculation the app produces is only as accurate as the readings and spec limits you provide. If a reading is entered, spoken, or scanned incorrectly — including misreads from photo scanning, live camera capture, or voice recognition — the resulting Cp, Cpk, Pp, Ppk, and control chart results will be incorrect too, even though the underlying math is correct.
The app includes features to help you catch this (flagging low-confidence readings, letting you review and edit before calculating, a read-aloud function for cross-checking against a physical sheet), but it cannot guarantee that every reading you confirm is actually correct. Always review captured data before relying on the results.
Before using CpK for a decision that matters, it's worth running a batch of historical data through it first — data you already have a known, trusted result for from another method or tool. Comparing what CpK produces against that known answer is the quickest way to build genuine confidence in it, the same way you'd validate any new measurement system before putting it to real use.
CpK does not replace calibrated measurement equipment, a formal quality management system, statistical training, or your organization's own quality procedures. It is a calculation aid intended to support someone who already understands what these statistics mean and how they apply to their specific process.
Any decision made using this app's output — including whether a process is capable, whether a part conforms to specification, or whether to adjust, accept, or reject anything — is made entirely at your own discretion. The app calculates numbers; it does not make quality decisions, and the developer is not responsible for the consequences of decisions made using them.
CpK is provided "as is," without warranty of any kind, express or implied, including but not limited to fitness for a particular purpose. The developer is not liable for any loss, damage, or consequence arising from the use of this app or reliance on its output.