Process Capability Calculator

To calculate a process capability analysis online, simply copy your data into the table above and then select the desired variable. The data can be in the following formats:

The calculated process capability is then clearly displayed.

The process capability indicates how well the result of a process fits the requirements of the process. By means of the so-called process capability index, process capability becomes quantifiable and the performance of the process can be determined. Just try the online cp and cpk calculator - it's easy. Of course, you can also create the most common control charts online with numiqo.

This calculator needs real sample data to compute Cp, Cpk, Pp, and Ppk. If your process inputs are uncertain rather than already measured, for example during early planning or tolerance design, model them instead with our Monte Carlo simulation software, which estimates the same Ppk and PPM measures from simulated data.

For counts of defects or defective units, use the attribute capability analysis with a Poisson or binomial model.

Process capability index

The process capability indices Cp and CpK are indicators for the statistical evaluation of a process in production engineering. They indicate how reliably the targets specified in the specification are achieved.

For the calculation of the process capability indices, several samples are taken from the process. The results table then displays the process capability indexes for the entire sample and those within the individual samples.

• Cp/Pp (Within/Overall): Ratio of the required tolerance window to the dispersion of the process
• Cpk/Ppk (Within/Overall): Ratio of the smallest distance to the mean value to the tolerance window and the scatter of the process

Normal capability analysis assumes that the process data can be adequately described by a normal distribution. Sample variance can also be calculated for non-normal data, but normal-model capability results and estimated defect rates may be misleading when that model does not fit. For non-normal data, select Non-normal in the calculator, compare the automatically fitted distributions, and assess their fit. See the non-normal process capability instructions for distribution-fit checks and overall Ppk and PPM results. Check process stability before interpreting capability.

Standard deviation within samples for process capability

For the calculation of the Cpk value, the standard deviation within the samples is needed.

Cpk is calculated by using the minimum of CPL and CPU. Ppk is calculated by using the minimum of PPL and PPU.

Process capability and process performance

After the standard deviation has been calculated, the process capability Cpk and the process performance Ppk can be calculated.

Cpk Calculator

With numiqo, you can calculate Cpk directly in your browser. Your data stays on your computer during the calculation.

Capability Calculator

The histogram shows the lower and upper specification limits as well as the target value, giving you a graphical impression what the capability of of your process is.

Within VS Overall

As explained above, samples of the process output are required for the calculation of the process capability. For example, 5 results are taken from the process at the beginning of each day, and this is repeated for 20 days. The process capability within the sample now uses the variance within each sample. The variance of all collected values is used to calculate the process capability of the entire sample or samples.