Measure process capability and centering using Cp and Cpk — so you can see whether your process consistently meets specification limits and where it sits relative to them.
Enter your specification limits, process mean and standard deviation on the left, then press Calculate.
Cp measures how much of the specification range your process variation occupies — assuming the process is perfectly centred. A Cp of 1.0 means variation exactly fills the spec range. Higher is better.
Cpk accounts for where the process mean sits relative to the specification limits. It is always equal to or lower than Cp. A large gap between Cp and Cpk means the process is off-centre.
Most industries require a minimum Cpk of 1.33 for an established process and 1.67 for a new one. A Cpk below 1.0 means the process is producing output outside specification limits.