X-bar R Control Chart Limits
Estimate subgroup mean and range limits with standard constants for subgroup sizes 2–10.
X-bar R Control Chart Limits
Browser-only calculations · No input data saved
Worked example results
- Subgroup size
- 3
- Grand mean
- 10
- Average range
- 2
- X-bar LCL
- 7.954
- X-bar UCL
- 12.046
- R LCL
- 0
- R UCL
- 5.148
Rounded for display only. Export includes the inputs, results, method and assumptions. Refreshing or leaving the tool clears entered data.
How to use X-bar R Control Chart Limits
- Load the worked example to see the required input format.
- Estimate subgroup mean and range limits with standard constants for subgroup sizes 2–10. Use consistent units, periods and definitions.
- Select Calculate, review the assumptions and export the result for your project evidence.
Formula and method
X-bar limits = grand mean ± A2 R-bar; R limits = D3 R-bar and D4 R-bar. Constants depend on subgroup size.
Interpretation and assumptions
Use equal-sized rational subgroups of size 2–10 in time order. At least 20–25 baseline subgroups are preferable. Establish range-chart stability before interpreting the mean chart; no full run-rule detection is performed.
Results support professional judgement. They are not a certification of process stability, a financial commitment or a substitute for study design.
Frequently asked questions
How do I use the x-bar r control chart limits?
Estimate subgroup mean and range limits with standard constants for subgroup sizes 2–10. Load the example first, then replace all inputs with consistent process data and select Calculate. X-bar limits = grand mean ± A2 R-bar; R limits = D3 R-bar and D4 R-bar. Constants depend on subgroup size.
What assumptions matter for x-bar r control chart limits?
Use equal-sized rational subgroups of size 2–10 in time order. At least 20–25 baseline subgroups are preferable. Establish range-chart stability before interpreting the mean chart; no full run-rule detection is performed.
Are my calculator inputs saved or sent to a server?
These native calculations run in this browser tab. Inputs are not sent to a server or saved by this calculator. Download the result if you need a record; leaving or refreshing clears the form.