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THE FEUTEX TOOLKIT

Process Capability Indices

Compare a stable process with specification limits using Cp, Cpk and one-sided capability indices.

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01 Your input
02 Your result
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FormulaCp = (usl-lsl)/(6*sd); Cpk = min(usl-mean,mean-lsl)/(3*sd); Cpu = (usl-mean)/(3*sd); Cpl = (mean-lsl)/(3*sd)
Sources and model references

Worked example

Inputs

Lower specification
0 value
Upper specification
12 value
Process mean
7 value
Process SD
1 value

Expected results

Cp
2 number
Cpk
1.666666667 number
Cpu
1.666666667 number
Cpl
2.333333333 number

Load the example in the workspace to reproduce these results. Display rounding does not change the underlying calculation.

How to use this tool

  1. Enter the labeled inputs using consistent units.
  2. Check the stated assumptions and calculate.
  3. Review each output and compare another input scenario.

Try this example

{
  "lsl": 0,
  "usl": 12,
  "mean": 7,
  "sd": 1
}

Accuracy and scope

Capability interpretation requires a stable process and appropriate distribution assumptions; negative Cpk is possible. Finite floating-point arithmetic; results can lose precision near singular or extreme inputs.

Is my data uploaded?

This tool runs locally in your browser. Input and output are not sent to a processing server. Copy or download your result before leaving the page.