Compare mixed-scale series with a combination chart

A combination chart can compare order counts with a return rate without pretending they share a unit. Use columns for counts and a line for percentages, then assign the percentage series to a clearly labeled secondary Y axis. Merely showing a second axis does not bind a series to it.

Prepare a deliberately mixed-scale example

Use LibreOffice Calc 26.2 desktop with English standard menus on Windows or Linux. These steps are documentation-based; native execution, screenshots and save/reopen behavior have not been verified. Work in a disposable ODS workbook, not CSV.

On a sheet named Monthly, enter A1:C5:

Month	Orders	Return rate
January	200	2%
February	240	3%
March	180	1%
April	300	4%

Enter the percent signs so the stored rates are 0.02, 0.03, 0.01 and 0.04. The order sum is 920. These are two measures, not quantities that should be added together. Keep the source table next to the finished graphic so readers can recover exact values.

Build the combination and bind the line

1. Select A1:C5 and choose Insert > Chart. Choose Column and Line, using side-by-side columns rather than stacked columns. Use one line if the dialog exposes Number of lines.
2. On Data Range, select series in columns, with labels in the first row and first column.
3. On Data Series, check that Orders precedes Return rate. Calc uses the last N series as lines. Verify Orders uses B2:B5, Return rate uses C2:C5, and categories use A2:A5; headers are names, not values.
4. Add a title such as “Orders and return rate by month” and a legend. Finish the wizard before assigning the secondary axis.
5. Double-click the chart to enter edit mode. Select the entire Return rate series, using Select Chart Element on the Formatting toolbar if its tiny values are hard to click.
6. Choose Format > Format Selection. In the Data Series dialog, on Options, under Align Data Series to, select Secondary Y axis and confirm.
7. Use Insert > Axes if the secondary Y labels need to be displayed. Add axis titles using the chart’s Insert > Titles: left is Orders; right is Return rate (%). Format the secondary axis numbers as percentages.

If the orders became a line, correct the series order rather than changing source column values. This is different from creating an ordinary column or line chart, where every series can use the same unit.

Make the scales honest

Right-click each Y axis and choose Format Axis. On Scale, turn off Automatic for the relevant bounds and use 0 to 400 for Orders and 0 to 0.05 for Return rate. Those are deliberate teaching bounds, not a universal rule. Check that 0.04 is labeled 4%, not 0.04% or 400%.

April should show 300 orders and 4%. A line crossing a column has no numerical meaning because the axes measure different things. Do not claim a common slope or causal relationship from this picture. When the audience could confuse the axes, use two aligned charts instead.

Change Monthly.C5 from 4% to 2%. Only April’s line point should move, to the same percentage height as January. The Orders columns and total 920 must stay unchanged. Restore 4%, save, close and reopen the ODS, and check series roles, both axis titles and bounds.

Recover from common mistakes

A nearly flat percentage line usually means it is still on the count axis. A second set of tick labels alone is not proof of series assignment. A missing point may be outside a manually fixed bound: inspect its source value before widening the scale. If the line includes a header or five values against four months, repair the role range through Format > Data Ranges while editing the chart. Keep the original source values intact while fixing presentation.

Official references

• LibreOffice 26.2 Calc Guide
• LibreOffice 26.2 Help

Sources were captured on 20 October 2026 and reviewed from retained snapshots. All outcomes above are expected checks, not a claim of native execution.