Cpk / Ppk Calculator
Calculate process capability indices Cp and Cpk from mean, standard deviation, and specification limits.
How to Use the Cpk Calculator
- Enter the process mean and standard deviation.
- Enter upper and lower specification limits.
- Click Calculate to see Cp, Cpk, and capability assessment.
Use Cases
- •Manufacturing process capability studies.
- •SPC and quality control analysis.
- •Supplier qualification and auditing.
Formula
Formula: Cp = (USL − LSL) / (6σ). Cpk = min((USL − mean), (mean − LSL)) / (3σ).
Frequently Asked Questions
What is Cpk?
Cpk measures how centered and capable a process is relative to its specification limits. A Cpk ≥ 1.33 is generally considered capable.
What is the difference between Cp and Cpk?
Cp measures potential capability (spread only), while Cpk accounts for both spread and centering of the process.
What Cpk value is required for Six Sigma?
Six Sigma quality requires a Cpk of at least 1.67, corresponding to 3.4 defects per million opportunities.