Cp / Cpk Process Capability Calculator

How well does your process meet spec? Measure capability with Cp and Cpk.

CurrentTarget

Upper spec limit (USL)

Lower spec limit (LSL)

Process mean

Standard deviation (σ) (σ)

Cp (potential) —

Cpk (actual) —

Sector target: 1.33

Cpk ≥ 1.33 is capable; ≥ 1.67 is the automotive target.

Values are calculated only in your browser; no data is stored.

About this metric

What is it?

How capable the process is of meeting spec limits. Cp is potential; Cpk is actual capability including centering.

How is it calculated?

Cp = (USL − LSL) / (6σ); Cpk = min[(USL − mean)/(3σ), (mean − LSL)/(3σ)].

How to interpret it?

Cpk ≥ 1.33 is capable, ≥ 1.67 the automotive target. High Cp but low Cpk means the process is off-center — center it.

How to improve it?

Reduce variation (SPC, DOE), center the process on target, and validate the measurement system with MSA.

Measuring is the first step; lasting gains come from implementing together on the field.