Quality Advisor

A free online reference for statistical process control, process capability analysis, measurement systems analysis, control chart interpretation, and other quality metrics.

Process performance indices

Process performance indices use sigma of the individuals .


pp formula

Pp for one-sided specifications

If you are using one sided specifications, use the following formulas to determine the Cp:

Upper specification:

ppu formula

Lower specification:

ppl formula


ppk formula


Zmin is the smaller of Zupper and Zlower.

Using sigma of the individuals:

z upper formula

z lower formula


pr formula

Easily perform capability studies with

Learn more   Try it!