Histogram maker

Select the column with your measurements in Excel, copy it (Ctrl+C) and paste it into the values box. The page detects decimal comma or point and draws the histogram at once. If there are several columns (one per machine or shift), each one becomes a group with its own color.

Start with automatic: the Sturges rule (k = log₂N + 1) works well up to a few hundred values; with thousands of values or long tails, Freedman-Diaconis usually draws a better picture. Then move the slider: the true shape keeps showing with 7, 10 or 12 bins; whatever disappears was an effect of the choice.

A symmetric bell means random variation. A long tail on one side appears with physical limits (zero, a stop) and times. Two peaks or a flat shape point to mixed machines, shifts or lots. A peak against one edge means parts sorted by inspection. A separate island calls for checking measurement, typing or a special event.

With fewer than 30 values. With so little data each histogram bar holds 2 or 3 values and the shape changes with the bins; the dot plot shows every value with no bin choice. In Automatic mode the page switches by itself.

x̄ is the mean; −3s and +3s lie three standard deviations from it. In a normal process 99.73% of values fall in that band. Compare it with LSL and USL: if the ±3s band goes past a limit, the process makes parts out of specification even when running normally.

It lets you see it: center, width and position relative to the limits. For a number (Cpk, Ppk, expected PPM), use the capability calculator, which the button below fills with your data. Remember the histogram does not show production order; stability is seen on a control chart.

Use Download PNG: the image comes out in light theme, on a white background and at three times screen resolution, ready for a report, a poster or a slide. The One-page report (PDF) puts the chart, the numbers and the shape reading on one A4 sheet.