SPC Control Limits Calculator
Calculate UCL, LCL, and center line for statistical process control charts.
How to Use the SPC Control Calculator
- Enter the process mean.
- Enter the standard deviation.
- Enter subgroup size and click Calculate.
Anwendungsfälle
- •Setting up X-bar control charts.
- •Quality monitoring in production.
- •Statistical process control training.
Formel
Formula: UCL = mean + 3σ/√n. LCL = mean − 3σ/√n. Center line = mean.
Häufig gestellte Fragen
What are control limits?
Control limits define the expected variation for a process. Points outside these limits indicate special cause variation.
How are control limits different from specification limits?
Control limits are calculated from process data and reflect actual variation. Specification limits are set by customers or design requirements.
What subgroup size should I use?
Common subgroup sizes are 4–5. Larger subgroups give tighter control limits and are more sensitive to small shifts.