Cpm
Taguchi capability index
Cpm = (USL − LSL) / (6 · √(σ² + (μ − T)²))
Cpm penalises any distance from the target value T, not only distance from the limits. It is useful where being on target matters, for example for mating parts.
Calculate it
Process Capability & Control Charts: Cp, Cpk, Pp, Ppk, PPM and confidence intervals with X-bar/R, X-bar/S or I-MR charts and all 8 Nelson rules.