Method
Equation
Ppk = min((USL − μ)/(3soverall), (μ − LSL)/(3soverall))σwithin ≈ average moving range / 1.128 for ordered individualsInspection
Cpk & Ppk Calculator from Measurement Data
Enter the drawing as nominal ± tolerance, then paste measurements. Dimvo calculates Ppk, estimates Cpk only for ordered data, identifies the limiting side and explains the screening result in plain language.
Decimal points and decimal commas are accepted.
Capability screening
Initial screening · stability not established
Outside a capable range
Estimated Cpk 0.829
Ppk
1.192
Mean
10.001
Off specification centre
0.001
Observed range
9.98–10.02
Limiting side
upper
Outside specification
0 of 10
The estimated natural spread extends beyond at least one specification limit. Ppk describes only the pasted dataset. Estimated Cpk uses successive moving ranges when production order is preserved. Confirm stability, distribution and measurement-system suitability before approval.
Small sample: 10 values can be useful for an early signal, but the index is sensitive to each new measurement.
Quick use
How to use this calculator
- Enter nominal size and ± tolerance, or switch to exact LSL and USL.
- Paste representative measurements in production order when possible.
- Read the margin warning and limiting side, then confirm stability before relying on the index.
Limits
Assumptions
- Ppk describes only the pasted dataset
- Cpk requires defensible within-process variation
- Indices alone do not prove stability or normality
Provenance
Independent calculation
Generated from the displayed equation and user inputs. This page does not reproduce a standard or third-party table.
Common questions
Frequently asked questions
What is the difference between Cpk and Ppk?
Ppk uses overall variation in the selected dataset. Cpk is intended to use within-process variation and is meaningful only after the process and sampling method are understood.
Does a high Cpk prove the process is stable?
No. Capability indices do not prove stability, normality, measurement-system adequacy or future performance.