Control chart and process capability calculator
Paste measurements in time order and enter lower and upper specification limits. The tool builds an individuals chart from moving ranges and calculates Cp and Cpk.
Individuals control chart
The line shows measurements over time. Horizontal lines mark the mean, control limits and specification limits.
Measurements and signals
| No. | Measurement | Mean | LCL | UCL | Outside control (1 = yes) |
|---|---|---|---|---|---|
| Fill in the fields above — the result is computed on this page. | |||||
How do I use this page?
- Paste measurements in their true time order.
- Enter approved specification limits.
- Inspect chart stability before interpreting Cp and Cpk.
What this page does not do: The model uses an individuals chart and sigma ≈ average moving range / 1.128. It does not replace measurement-system, normality, autocorrelation or SPC plan reviews.
Further reading
Theory — how do control limits differ from specification limits?
Control limits describe the variation actually observed in the process and are estimated from the moving range of consecutive measurements, while specification limits come from requirements and should not be confused with them. Cp compares the width of the specification range to the process spread, and Cpk additionally accounts for how far the process is shifted from the center of that range. The calculator builds an individuals chart from the measurements you paste in time order, together with the given LSL and USL.
Frequently asked questions
Are LSL and USL control limits?
What Cpk is good?
See also
A/B test calculator
Compare two proportions in an A/B test. Calculate conversion rates, difference, uplift, z score, p value and c
A/B test planning — sample size, MDE and duration
Plan a two-proportion experiment, estimate detectable effect and traffic duration.
ACF and PACF autocorrelation calculator
Calculate ACF and PACF across time-series lags. Review the chart, reference bounds and coefficient table.