%Off-Target is a diagnostic measure that represents the percent of the specification range the mean falls from target. This measure is calculated by the following formula.

where

- USL is the Upper Specification Limit,
- LSL is the Lower Specification Limit,
- T is the Target, and
- is the sample mean from all combined data.

As the process average departs from target, P_{pm} is reduced. The figure below graphically displays the relationship between P_{pm} and %Off-Target. The resulting P_{pm} is shown for four levels of P_{p} (at infinity, 3, 2, 1.5, 1) as the offset from target varies. The highest line represents a process with a standard deviation of zero (P_{p} at infinity). If a process is running with a mean 10% off target, the largest P_{pm} that may be achieved is 1.67. At 30% off target, the largest P_{pm} that may be achieved is 0.56.