SIGMADESK – Online Control Chart Generator
Built for Real SPC Work
SIGMADESK is an online SPC software platform that lets you build, analyze, and interpret control charts directly in your browser. It covers the full range of chart types that quality practitioners actually use in the field.
Variable control charts for continuous measurement data:
- I-MR chart (Individuals and Moving Range) — the right choice for processes where you measure one unit at a time, or where subgrouping is not practical.
- Xbar-R chart (Mean and Range) — the workhorse of SPC in manufacturing, used when you collect small subgroups and want to track both the process mean and within-subgroup variation.
- Xbar-S chart (Mean and Standard Deviation) — preferred over Xbar-R for larger subgroup sizes, where the sample standard deviation gives a more efficient estimate of spread.
Individual Chart — every measurement plotted separately
Attribute control charts for count-based data:
- p chart — monitors the proportion of nonconforming units in a sample, ideal when your subgroup size varies from inspection to inspection.
- np chart — tracks the number of nonconforming units when sample size is constant.
- c chart — counts defects per unit on a fixed inspection area or time window.
- u chart — tracks defects per unit when the inspection area or opportunity varies.
P-Chart — proportion defective with variable subgroup sizes
Each chart type follows the correct statistical formulas, applies the right control limit calculations, and displays both the main chart and the range or standard deviation sub-chart where applicable.
A control chart is only as useful as the analysis behind it. SIGMADESK is built with that in mind.
Western Electric Rules are built in. You can toggle rule detection on or off and see exactly which data points trigger which patterns — Zone A violations, runs above or below the centerline, trends, and more. These are the same rules taught in every Lean Six Sigma certification and used in serious manufacturing environments.
Stages let you define breakpoints in your data — before and after a process change, across different production shifts, or spanning a kaizen event. Control limits recalculate independently for each stage, which is exactly how SPC should handle process changes. This is a feature typically found only in paid software.
Process capability analysis is integrated directly. Once your process is confirmed stable through control chart analysis, you can move to Cp, Cpk, Pp, and Ppk calculations in the same workflow — no switching tools, no re-entering data, just enter your specification limits.
Flexible data entry means you are not locked into a rigid format. Whether you are working with individual measurements, subgroups of varying sizes, or attribute inspection counts, the data grid adapts to your chart type.
And you'll discover many more features of SIGMADESK throughout your SPC journey.
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