# Calculate process capability or reliability | Free template

Process capability is a free template to calculate the capability or the ability for a process to produce within specified tolerance ranges. Process capability is a process ability to meet design specifications.

A process is in statistical control does not need to produce the units within the tolerance range for the product according to specification. In order to measure whether a process is producing units within the specified tolerance range according to specification, process capability has to be measured.

In this template two measures are calculated for process capability, process capability ratio (PCR) and process capability index. To calculate process capability of a process you must know the customer's requirements or the design requirements for the product, these requirements are provided as an upper and a lower limit. Furthermore, one must have information on the process mean and standard deviation for the measurement of the product during production.

The process capability ratio is measured by comparing the difference between the customer's upper and lower requirements by 6 standard deviations for the process. Process capability ratio measures the relationship between customer requirements and 99.73% of the variation in the process. If the process capability ratio is 1 then the variation in customer requirements are as large as the variation in the process. If the process capability ratio is greater than 1 then the variation in the process is less than the variation in customer requirements. Even if the process capability ratio is 1 it does not mean that the mean value for the process is the same as the mean value for the customer's requirements for the process to be capable.

Process capability index takes into account also the mean of the process and is calculated as the minimum value of the customer's upper requirement minus the process mean value in relation to 3 standard deviations and the process mean minus the lower customer requirements in relation to 3 standard deviations. If the process capability index is 1 that means that the process meets customer requirements in 99.73% of the cases. A process should have a process capability index of 1 or higher for us to be able to say that the process is capable or reliable. If the process capability index is less than one such a process does not meet the requirements of the customer and if the process capability index is greater than one a process exceeds customer expectations.

You can use this template to measure processes reliability or capability.
Updated: 01/01/2015 | Created by All-templates.biz