The process capability is a measurable property of a process to the specification, expressed as a process capability index (e.g., Cpk or Cpm). The output of this measurement is usually illustrated by a chronological control sample, histogram and calculations that predict how many parts will be produced out of specification (OOS).
Here you get this free process capability template 20170716.xlsm to calculate all process capability figures you need.
If you want that i make some adjustments for you contact me.
cpk calculation excel template
process capability excel template 20150102.png
The calculation procedures refer to this books:
Understanding Statistical Process Control
SPC Simplified: Practical Steps to Quality
If you want to to have a more scientific look on process control you can check this discussion in the minitab blog. Another way is to look on the homepage of ASQ.
Please feel free to contact me, if you have some suggestions to improve this page (roland.schnurr@sixsigmablackbelt.de) or if you want to get a free copy of the excel sheet.