Excel Chart With Two Y-Axes: How to Make One

To make an Excel chart with two different y-axis values, select the chart, choose Chart Design > Change Chart Type > Combo, and select Secondary Axis for the series that needs its own scale. For example, plot sales as columns on the left axis and a percentage as a line on the right; the two axes can use different units and ranges.

What a secondary y-axis does

A standard chart usually has one vertical value axis, also called the y-axis. Every series plotted against that axis shares its scale. That works when the values are comparable, such as monthly sales for two regions, but can make one series hard to see when the values differ greatly. A secondary y-axis adds a second vertical scale on the right side of the chart. Excel can plot one or more series against that scale while other series remain on the primary, left-side axis.

The key distinction is that the axes have independent scales, not that Excel converts one set of data into another. If the left axis shows dollars and the right shows a percentage, Excel plots the dollar values against the dollar scale and the percentage values against the percentage scale. The chart still uses the values in the worksheet; assigning a series to the secondary axis does not change its cells or calculations.

A common example is monthly revenue and conversion rate. Revenue might range from $20,000 to $180,000, while conversion rate ranges from 1% to 8%. With one axis, the percentage line may sit close to the bottom because its values are small relative to revenue. Separate axes make both series visible, while the chart’s axis titles explain what each scale means.

When two y-axes are useful

A dual-axis chart is most useful when two related series have different units or substantially different magnitudes, and readers need to compare how they change over the same categories or time period. Common pairings include:

Revenue and profit margin, with currency on one axis and percentage on the other.
Units sold and average selling price, when the chart is intended to show their movement over time.
Website visits and conversion rate, when both series share the same dates.
Temperature and rainfall, if the chosen chart makes the distinct units and scales clear.

The chart is less suitable when the series have no meaningful relationship, when the audience may mistake one scale for the other, or when the point is simply to compare their absolute sizes. Two independent axes can make unrelated trends appear to move together. If readers need to compare values directly, use the same scale where practical, or use separate charts with clearly labeled axes instead.

Create a combo chart with a secondary axis

In Excel for Microsoft 365 on Windows, a combo chart is usually the clearest approach because it lets you choose both a chart type and an axis for each series. Arrange the data with categories—such as months—in the first column and each data series in a separate column, with headers in the first row. Select the complete table, including headers, before inserting the chart.

Choose Insert > Insert Combo Chart. If that button is not available or you already have a chart, select the chart and use Chart Design > Change Chart Type.
In the chart-type dialog, select Combo. Excel displays a chart type choice for each series and, where supported, a Secondary Axis checkbox.
Choose an appropriate type for each series. A frequent choice is Clustered Column for a volume or currency series and Line for a percentage or rate.
Check Secondary Axis on the series that should use the right-hand scale. Leave the other series on the primary axis.
Select OK, then add titles and check that the two vertical axes identify the correct units.

For instance, suppose a table has Month, Revenue, and Conversion Rate columns. Set Revenue to Clustered Column on the primary axis, and Conversion Rate to Line with Secondary Axis checked. The chart then has revenue values at the left and percentage values at the right. If Excel assigns the months or series in an unexpected direction, use Chart Design > Switch Row/Column and review the result.

Excel for Mac has a similar chart workflow through the chart design controls, though dialog layout and ribbon placement can vary by release. Excel for the web has fewer chart-editing controls than the desktop app in some situations. If you cannot find the combo or secondary-axis options in your browser, open the workbook in the desktop version of Excel to set up the chart.

Assign an existing series to the right axis

You do not have to rebuild a chart to move one series. Select the chart, click the data series you want to move, and open its formatting options. On Windows, right-click the selected series and choose Format Data Series. In the formatting pane, under Series Options, select Secondary Axis. Excel places that series against the right-side scale.

Take care to select the series rather than an individual point or the chart background. If the pane shows point-specific formatting or a different set of options, click the series again or use the chart’s selection controls to select the intended series. You can also use Chart Design > Change Chart Type > Combo to set the axis and chart type for every series in one place. That method is often easier when you are changing several series at once.

Set the scales and label both axes

Excel chooses axis limits automatically, and its choices may not make the chart easy to read. To review a scale, right-click the relevant vertical axis and choose Format Axis. In the formatting pane, use Axis Options to inspect the minimum and maximum bounds and the major unit. Automatic bounds are convenient, but you can enter fixed bounds when a consistent range is important across multiple charts. A fixed range should be chosen carefully: cutting off meaningful values or exaggerating small changes can distort the story.

Make the units unmistakable. Select the chart and use Chart Design > Add Chart Element > Axis Titles to add primary and secondary vertical axis titles. Name them specifically, such as “Revenue (USD)” and “Conversion rate (%)”, rather than just “Value.” Check the number format on each axis as well. Currency symbols, percentage signs, and sensible decimal places help readers identify the scale without guessing.

Use color consistently: for example, make the line, its legend entry, and the right axis labels the same color, while keeping the columns and left axis visually distinct. A clear legend helps, but it should not replace axis titles. If the chart has many series, labels and colors can become crowded; reduce the number of series or split the information into separate charts.

Common problems and how to fix them

The series is nearly invisible. Confirm that it is assigned to the intended axis. If it is on the correct axis, inspect that axis’s bounds and number format. A percentage stored as 0.05 is normally displayed as 5% when formatted as a percentage; formatting and underlying values should not be confused.
The secondary-axis option is missing. Select a data series, not the chart area, and try Format Data Series or the Combo chart dialog. Some chart types do not offer the same axis choices, so changing the series to a compatible 2-D type may help.
The chart looks different after changing an axis. The secondary scale is independent. Excel may select different automatic minimum and maximum bounds, which changes the apparent height or slope of a series. Check both scales before interpreting the visual comparison.
The wrong series appears on the right. Reopen the Combo dialog and verify the checkbox beside each named series. Also check that the source data headings are correct; the series name shown in the chart is based on the selected source range.
The chart is hard to explain. Add units to both axis titles, simplify the legend, and consider whether a single chart is the right format. A chart that needs a long explanation to distinguish its scales may not be serving its audience.

Why dual axes can be misleading

Two y-axes make it possible to see series with different scales, but they can also create a false impression of correlation. Because each axis can be scaled independently, changing the minimum or maximum can make two lines appear to track closely, cross at a chosen point, or diverge—even though the underlying data have not changed. A visual intersection between lines on separate scales does not mean their numeric values are equal.

Use the chart to show the intended comparison, not to imply more than the data support. Label both scales, choose bounds that make sense for the subject, and explain the relationship in a caption or nearby text when needed. If the main question is whether two measures move together, consider showing the underlying values in a table or reporting an appropriate statistical comparison rather than relying on line overlap alone.

A useful check is to ask a reader unfamiliar with the worksheet what each axis measures and what conclusion they take from the chart. If they cannot identify the units or believe the two series share a scale, revise the labels or choose a different chart design.

Alternatives to a second y-axis

A dual-axis chart is not the only way to compare series with different units. The best alternative depends on the question:

Separate charts with aligned dates: This preserves each measure’s natural scale while letting readers compare timing. It is often clearer for reports and presentations.
Small multiples: Use several similarly formatted charts, one per measure or category. Matching layouts make patterns easier to compare without sharing a y-axis.
Indexed values: If the goal is to compare relative change, convert both series to an index such as 100 at the starting period. This removes the original units, so label the chart as an index and retain the original data elsewhere.
A single axis with a common unit: If both series can be expressed meaningfully in the same unit and range, a shared axis avoids the interpretive risk of two scales.

Do not choose an alternative merely because it looks simpler. For example, indexing is helpful for comparing proportional growth, but it hides absolute size. Separate charts make units clear but may make direct timing comparisons less immediate. Match the chart to the question the reader needs to answer.

Frequently Asked Questions

Can an Excel chart have two y-axes?
Yes. Excel charts can use a primary vertical axis on the left and a secondary vertical axis on the right. Assign a series to the secondary axis through the Combo chart dialog or the Format Data Series pane.

How do I put a line on a secondary axis in Excel?
Select the chart and open Chart Design > Change Chart Type > Combo. Set that series to Line and check Secondary Axis beside it, then select OK.

Can I use different units on the two axes?
Yes. For example, one axis can show dollars and the other percentages. Add explicit axis titles and suitable number formats so readers know which values belong to each scale.

Why does the line change shape when I add a secondary axis?
The right axis uses its own scale and may have different automatic bounds from the left axis. The plotted data have not changed, but the visual proportions can. Review both axes’ minimum and maximum values before drawing conclusions.

Can I add a secondary axis without changing the chart type?
Often, yes. Right-click the selected series, choose Format Data Series, and select Secondary Axis under Series Options. If the option is unavailable, use a compatible chart type or the Combo chart dialog.

Try it: the Percentage Formula Generator: percent of, percent change, increase and decrease, with the formula.

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Sources: Function behaviour and menu paths: Microsoft Support documentation for Excel. Method & sources

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