Enter the upper specification limit, lower specification limit, standard deviation, and process mean into the calculator. The CPK calculator will evaluate and display the process capability index of those values.

## CPK Formula

The following formula is used to calculate the CPK, or process capability index, of a given set of data.

CPK = Min [(USL – mean/3 * std.),(mean-LSL/3*std.)]

- Where CPK is the process capability index
- USL is the upper limit
- LSL is the lower limit
- std is the standard deviation

## CPK Definition

CPK is defined as the process capability index and is a measure of the ability of a process to produce objects to a customers specifications.

## CPK Example

How to calculate CPK

**First, determine the upper and lower limits.**These are the upper and lower limits of the specifications.

**Next, determine the mean of the data.**This is will be the average of all data points.

**Next, determine the standard deviation.**This should be the standard deviation of the sample set.

**Finally, calculate the CPK**Calculate the process capability index using the information from above and the euqation.

## FAQ

**What is CPK?**

CPK is a term that standards for process capability index. The process capability index is a value used to measure the ability of a process to produce to a customers specifications.

**How do you improve CPK?**

Improve CPK by moving the upper and lower limits closer to the mean.